"Casual" actually rather means playing non-competetive (means no clan matches, actively playing Strat or active clan training, anything competetive, looking for becoming the best) and only playing for fun. That could mean 24/7 though.
Or you see "casual" as playing the game whenever you have time (in that case rarely), like an hour a week or similar.
But once a day, isn't rarely.
My shortest time to retire was 4 days. I played too much. After that I really reduced my gaming time in total. But a retirement in 1 - 2 weeks is no problem with 3 - 4 hours a day. always x1 is wasted time if you aim to retire quickly.