I know in the indie game field, ~95% of lifetime sales happen in the first year. But to be fair, they typically don't have the similar marketing power as a AAA. I'd venture 60% (gut/instinct). There must be a good reason for running sales even in the long term. That could also be skewed when you think of in-game purchases too. Cheaper year 2 or 3 purchases could be pushed for if they're banking on in-game purchases.

Either way, pretty sure someone broke open an expensive bottle of champagne for a 1 year mark.