Having used M-Seal over the last 6-7 months I can vouch that durability isn't an issue, as David said 2 coats with about 30 mins between (this is just to even out the coating thickness more than anything) followed by a coat of good quality wax will last for ages.
I have clients that had their cars done just before the JAE, still beading water with little or no maintenance since doing them. However I would always recommend a top up coat of wax every 4 weeks, and if this is done after a proper wash (not using over strong shampoo) then the M-Seal won't actually be affected by the elements and can last even longer.
I can't comment on EGP as not used it.