Hello,
Is there any sense for POS with ~50 coins in the wallet?
How long should I wait to get something?
i think it can be possible. But you should keep all coins in one input.
1- put all coins in one input
2- after 28-29 days launch wallet and unlock for staking. and wait

1. So it's not necessary to keep wallet opened all the time for staking?
2. It's enough to open it once a month and wait for payment?
1. yes, if u want to stake all time: wallet should be opened and unlocked (at least for staking).
2. not always, since the probability of finding a block depends on the staking time.