any four season campers?

We have had our '98 2720SL for a while and are at a stage to consider long distance and four season camping. While distance isn't really the issue (we've done a NC to IA circuit for example), the four seasons is. We are considering an Alaska tour-through Canada as one possibility. So who has done it? what were the concerns (comforts, hardships, etc). We are really serious about the trips but also concerned that we might have to step up to a 5er to get it done safely, comfortably and successfully. TV is not a problem as we just stepped from our F150 (which towed the TM really easily) to a 2007 F250 SuperDiesel with integrated tow and brake package. SO we really are focusing on the TM, it's ups and downs in doing cross-country and more extreme weather conditions. Any help would be appreciated. Thanks, Richard & Teme