does it grows unlimited?
can i shrink it somehow?
Yes, wallet.dat will continue to grow as you receive transactions.
Is it really a problem? Rarely it will get above a few MB for the typical user.
One method to "shrink" a wallet is to create a new one and send funds from the old one to it. Though if you ever receive additional payments to addresses in the old wallet they don't automatically go to the new wallet.
Are you instead referring to the blockchain (the blk*.dat files?) That is growing continuously and is nearing 1 GB of storage. (Though for most computing systems, 1 GB is a trivial amount of storage)
