That's too vague of a question since everything depends on how much health they have before/after the combo i.e. how much impact that combo has on the round.
If it's to close out the round or to bring them close to 0% health then any means necessary to pay for that combo is worth it.
But if they're going to end up with 30-40%~ health left and you're entirely out of resources after then I would prefer to save them up so I'd be able to close them out in one swipe. You don't want to put yourself in a situation where your options are much more limited than your opponents.
Learning to weigh out when to use meter and when to not use it comes with experience, matchup knowledge and player knowledge all put together.
Say I'm playing against someone who I know crumbles easily when low on health I'd never hesitate to put them in that situation, but if I'd play against someone like Daigo who is very good at clutching it out when low on health I'd definitely want to close out the round entirely rather than leave him with low health.
So what I mean to say is that you can't really say there's a universal way of thinking when it comes to meter management, it's something that has to be decided on a case-by-case basis.
If it's to close out the round or to bring them close to 0% health then any means necessary to pay for that combo is worth it.
But if they're going to end up with 30-40%~ health left and you're entirely out of resources after then I would prefer to save them up so I'd be able to close them out in one swipe. You don't want to put yourself in a situation where your options are much more limited than your opponents.
Learning to weigh out when to use meter and when to not use it comes with experience, matchup knowledge and player knowledge all put together.
Say I'm playing against someone who I know crumbles easily when low on health I'd never hesitate to put them in that situation, but if I'd play against someone like Daigo who is very good at clutching it out when low on health I'd definitely want to close out the round entirely rather than leave him with low health.
So what I mean to say is that you can't really say there's a universal way of thinking when it comes to meter management, it's something that has to be decided on a case-by-case basis.