So I'm leveling up my medic, to the point where I need to decide if I want to drop the huge pile of cert points on the 'revive' grenade. It'll be either that...or the 'heal' grenade and a couple weapon upgrades (it's much cheaper)...or a PILE of weapon upgrades for my engy and medic. Seems like it might be a decent way to earn its cert cost back in no time by massive group revives, but...well, you only really get 1 grenade at a time. That's not much! Do either of these grenades stick around for a long time or something to make them really useful, or...?