Bonus points if your cleric buddy never EVER has to sleep, or even rest.
See: necropolitan, neraphim, and/or warforged.
He still needs to regain spells somehow. But i see the general gist of things. Invulnerable wizard sits in his fast time plane and projects awesome at the mere mortals beyond. Warforged are out, as are any setting specific thing, the campaign is a modified epic dark sun. The most we can get away with is necropolitan as undead infest the place. I presume necropolitan is the only way I do not age to death?
As if.
When casting the spell Genesis, you decide "all aspects" of the plane you create. While not explicitly stated, it is heavily implied you can also control the flow of time.
You simply decide that your plane is timeless, that it's occupants do not age, and time spent there does not count against them when they go somewhere else (to prevent the rapid onset of crumbling to dust).
The cheese comes into play when deciding to use a hyper-accelerated time, such that 24 hours on your plane is equal to 1 second on the Material Plane, or however cheesy you want.
Not sure how it relates overall to being invulnerable, but if aging to death is a concern of yours then Elan will work. Note though that their immortality is a result of an errata to the Age Category table in XPH that removed their maximum age.
Then there is always lichdom, necropolitan, or
this handy thread.Clerics don't have to rest to regain spells. They regain them 1/day at a specific time of day.
+1 to this. Clerics need 1 hour in prayer change and regain their spells. That's it.