I'm asking because I would like certain KT1 addresses return the funds back to the owner after a certain amount of blocks
No, there is no built-in function for this. However, it can be accomplished with a smart contract, that when called by the owner after a certain deadline returns its balance. Currently, the deadline must be specified as a timestamp, but future versions of Michelson may include a
LEVEL instruction (see this merge request). It returns the block level of the current transactions, and so could be used to implement the behavior your describing.
However, there is currently now way of "expiring" or "suiciding" a contract in Michelson. Deployed contracts stay on the block chain forever. However, you can implement the contract so that after a certain deadline (specified using a timestamp or the
LEVEL instruction described above), all incoming calls are rejected.