As Lynall said, you'll be able to see if they are leaking as the seals on the swivel ball will build up with black gunge. This is the one shot grease leaking out passed the the broken seals on the ball and collecting crap. If this isn't apparent, then they'll be ok. If you're still worried, do as Hicap phil said and put half a tube in each swivel.
Heat the grease pouch up in hot water to enable it to flow more easily. IIRC, the wheel needs to be turned out over, so the inner part of the swivel ball clears the fill hole, so the grease can drop straight inside the ball. If you don't do this and try to squeeze the grease straight in, it will ooze straight back out and down the back of the wheel assembly.