For example. If a shield was earnt during an attack, you could disable it and save it for a later time.
so for instance, if a 10 hour shield was earned, you could turn it off and save up another 2 hours, and use the total 12 for a time when you want/need it.
i suggest a button of some sort in a menu when you click shield saying something like "preserve shield", which would allow us o save the shield for another time.

