Not very often. There're games for you to join in, but the mods don't give out rewards until really late. Most of the time, you don't really do anything, so it's just collecting and collecting and collecting and trading.

It's not time-consuming or anything, unless you let your updates and rewards pile up. Errr, you'll definitely need to check your email for notifs [since you say you don't have a habit of doing that] or else you'll miss out on rewards.