I tried doing a search but couldn't find anything that answered my question. There are plenty of 'how much have you got' threads though, this is not one of those 
I struggle to understand if savings should be cumulative, or eventually spent, or a mix of both. You often see 20% of take home pay quoted as how much you should save, but is that the cumulative suggestion?
We save for Christmas/birthdays on a monthly basis but obviously that is all spent throughout the year. We also save for general rainy day things and try not to dip into that pot.
If you save regularly, what do you try to aim for? Is there a certain amount you save that must not be touched, and if so what proportion is that of everything you save?