Really "Tough" Encounters - Include in Adventures or Not?

From both a player's perspective and a DM's perspective, should "really tough" encounters, those that have an EL of the party's level + 5 or greater (e.g. like + 10) ever be incorporated into an adventure? These are encounters the party is never meant to have a chance at beating. If they are included, the DM, of course gives clear indications that they are "too tough" and or a way for the party to get away.

Before I give my opinion, I want to hear what others have to say.

Hard isn't too bad and are not impossible to beat. I stick to the xp levels in the slave ship campaign and it's challenging but not impossible. If you want the players to run away then make it obvious. Minions in the game confuse things because what used to be an obvious impossible encounter now looks possible if a bunch are minions. How to fix it? Do what WotC DMs do. Indicate which ones are minions instead of hiding them, or state which ones are not minions. Also calling out Elites and Solos help Players decide if they need to run. Having a figure on the table is different than you describing how bad ass, or weak, something looks.

My opinion is probably different than most, but I think encounters of Level+3 or +4 should be rare and reserved for bosses.

Normal encounters should be Level-1 to Level+2 (including terrain features and other specials).

Note:
I haven't posted comments on the last War adventure because I wanted to see what others thought. To me... It didn't feel like one or two of the encounters had their EL counted correctly... They were much higher than listed. (Archers with an area burst Daze (save ends) vs 6th level)?

There are times for tough encounters and every once in a while there are times for impossible encounters. I do believe that there has to be clear warnings for both of them so that tactics and expectations can be adjusted.

A tough encounter to me would be one the PC's are expected to use more than normal resources but it is possible to beat. Be it dailies, items, favors, or other resources the party can win through. I would not expect a few bad rolls (up to a point) to result in a TPK or similar situation.

An impossible encounter for me is one that has certain avenues that are actually impossible to beat. However for that to be included in the game there needs to be other avenues that are possible and those avenues should be clearly spelled out.

An example I could come up with would be the PC's on trial. Obviously you can't fight your way out of that one but there is a clear diplomatic/investigation path available to the PC's. It would need to be made clear in the setup that there are far too many guards and wards for them to even try fighting. In this case I would say that even if the trial doesn't go your way due to bad rolls or whatever then the failure option is something like doing errands for the king to pay off your debt.

Even an even level encounter can be extremely difficult or artificially inflated if the environment is unfavorable to the PC's. Take 10 archers and place them all within charge distance of the PC's and it is an easy encounter. Take the same 10 archers and place them all over 20 squares away through difficult terrain and on inaccessible ledges and it becomes a slaughter.

In short tough and impossible encounters should be in the game however they should be rare and only be for plot devices. They should be made clear that they tough or even impossible by certain methods and further the DM should be flexible in the methods used by PC's since people will usually do something unexpected.

Yep, read all of the above; some good thoughts. I'll mostly (but not always) keep the typical encounters on an adventure between EL-2 and EL+3. Because I view the skill level of the players in our gaming group to generally be higher than what I think is the WoTC average, I admit I do tend toward slightly higher EL's than what is right out of the book; and by slightly, I mean about +1.

I also do try to take the terrain and any allies the party may have into account when I note the "actual" EL of an encounter in my notes. Highly agree with Chris that terrain can really throw off the actual EL of an encounter. The signature battle for a session will typically be a "boss" encounter of EL+3 or EL+4, a tough, but not nearly impossible battle.

In the WAR! series, I've been thinking of how to work in encounters of EL+6 or even higher, if they could somehow add to the story and if they'd be any fun at all (or serve some other purpose). In this series, more than other series I've written, it would be very plausible for the small party to encounter an entire column of enemy troops. If I ever did have the party encounter an "impossible" encounter, I agree that the party should be given very clear messages that the monsters in question are way tougher than the party can possibly handle or the party should be given a non-combat solution to the encounter (e.g. flee, diplomacy, surrender, etc.).

The only caveat I would put on some of the non-combat options is be aware of the impact it can have on player morale/outlook. Surrender is a viable option in many situations and it can lead to some good sessions for getting out of that situation but for me it is always demoralizing to surrender. It just doesn't seem right somehow for my "legendary" PC to be stuck in a dungeon. I know that is a personal problem but just don't expect my first action in the face of overwhelming odds to be surrender. Even though it maybe the best option I will usually try something else first.

Yeah, I wouldn't ordinarily consider surrender an option either but I did throw it out there because in some situations it might fit in. In the BoM, recall the party made friends with (did a huge favor for) the Warden of the Prison. Several sessions later, there was a very, very, tough encounter and if any of the PC's had been captured or surrendered, I did have it written into my notes that they would have been transfered to the local prison, the warden would have recognized them and then staged the PC's "breakout" to even the score.