If you're getting a good lead (I'd say when there's less than 25 points left usually), your team's getting splatted, and you can cram in a few more points you should usually go for it, but if the enemy team isn't pushing you back, and you got the shield pop, it might be best to stabilize and wait for your teammates to respawn, for someone to get a kill or special before pushing the rainmaker again, or for the enemy team to get distracted, that way you'll gain more points, and your push will last longer.
But don't overheat and always go for kamikaze plays, especially at the end of the game it can be easy to panic and desperately try to score, but I'd say it's best to be patient when that happens, since the enemies might also panic and feed to preserve their lead
Also depends on if the enemies have a kraken weapon, if they get their kraken it's pretty unlikely you'll be able to score that far, so then it's sometimes better to push really fast before they get it
And if you're like, one point away from lead or something, and you're in a 3v4, don't pick up the rain right away, since the enemies will be expecting it and you might just get insta splatted for it, stay patient
tl;dr uhh, it depends