Time on the metaplanes, how long can you be away? Options

[The Dread Polack]

A magician can normally project for a number of hours equal to his Magic attribute. Does this apply to time spent in the metaplanes? Does this mean an initiate with a magic of 5 has to complete any quests in under 5 hours?

As a player, my whole party went on an astral quest to a series of planes over the course of what felt like a few days by way of an astral rift. When we returned to our bodies, no time had passed back in the physical world. This seems like a perfectly legit way to do it, but I can't find any official word on how it's supposed to work.

The reason I ask is that I had the idea of having an NPC magician (whom the party is trying to rescue) astrally project and get tied up on the metaplanes, at which point, his body will begin to starve and dehydrate. The PCs will have to both protect his body and try to sustain it until he can get back or they can find his spirit.

Alternately, I was thinking of having his spirit get trapped (most likely intentionally by some toxic shamans in a mana barrier) on the astral plane. Is there a way that his spirit can be preserved so that it can last longer than 5 hours outside of his body?

Thanks.

The Dread Polack