I am assuming since you have a vacuum sealer you also have room to store these in a freezer.

Do they lose potency over time, yes. But in my personal experience they are still usable.

You may just have to increase amounts based on the previous batch.

If you are devoloping recipes to enter in a competition use the freshest hops you can for consistency.

If you are just brewing to experiment and drink these will work.

If you are really worried about not using enough and they won’t work for you. Look for local clubs to share/trade.