My 4e D&D campaign is designed to last the 5.5 years (early 2011 to late 2016) it takes to get from level 1 to level 30 at around 4 sessions to level and playing 3 hours fortnightly, currently at
level 25 after 92 sessions and would expect something like 110-115 sessions total.
I've run a bunch of ca 30 session, ca 2-year campaigns in the 2000s. My current Pathfinder
campaign is most like that, next Sunday should be the last session, session 34, having
run January 2014 to end September 2015, 1 3/4 years.
My Classic D&D Karameikos campaign is a weekly sandbox running since start of April 2015, PCs currently around 5th level mostly, not sure when it will end, basically should run indefinitely while I have
players, the way BECM is I could run it to 36th level no problem.
My 5e D&D online Wilderlands sandbox started in March 2015, building on prior campaigns (1e, LL, 4e etc) back to ca
2009, currently weekly. 35 sessions and PCs ca level 7-8 currently. Judging by past experience this will run until there's a TPK; if no TPK I'm happy to run it indefinitely and it looks to have a lot of legs. In the 5e rules PCs cap at 20th
level and get GM-mandated Boons after that, which looks very manageable - I'd probably
say "you can have this Boon or can choose a Feat in lieu", per the sidebar in the 5e DMG.
Is speed of levelling an issue in 5e sandbox? Not really - it seems slow enough in my two sandbox games (5e is super-fast at low level, slows down a lot from 5th/6th, should speed up from 11th. The Pathfinder group have often levelled up in 1-2 sessions though, that felt too fast to me. I guess my
5e group should reach 20th long before the Classic group reach 36th, but in both cases
it's going to take a long time, maybe some time in 2017 for the 5e group. If the 5e player characters avoid TPK, reach max level, and
want to retire, that would be fine - but I want to give them a chance to shape the world
for future campaigns.
Read more: http://www.enworld.org/forum/showthread.php?469073-How-fast-do-you-play-D-amp-D/page3#ixzz3mXo1hcGH