Choice of expiration depends on if doing long or short Butterflies (rate of time decay).
Do 3 legged Butterflies (all puts or all calls) to avoid add'l frictional costs.
Put and call Butterflies with same strikes and expiration are synthetically equivalent (similar P&L).
Close out point based on outlook for the underlying as well as amount of P&L at that later date. For example, it's silly to stay in a position with weeks to run for 10% of the final profit. Book em Dano.
Paper trade before plunking down the cash. Get a feel for how they behave as well as what suits your comfort zone.