Bf and stash

Hi mummies. I bf baby as well as pumping bout 1-2 times a day. My concern is when baby gets bigger (currently 3mo), they tend to sleep throughout the night, do I need to pump or just let it be till the next dl feeding? And by building up stash (should I consider to pump at night), the stash can only be kept for 6months (at -18dg) - concern here is, if I able to bf till that period or pass 6 months, doesn’t the stash goes to waste or how do I utilise the stash yet bf at the same time or do I need to discontinue pumping and building stash?