K.P.
The banks have learned their lesson... why are you in such a hurry to purchase again? There is a reason why they want to wait a third year... you need "three data points" to create a trend pattern, meaning that having "two good years" does not create an "upward financial trend" with respect to your income and credit.
What you "want" to do is irrelevant. The BEST thing you can do is work your tails off to reduce all of your debt (including "good debt") and continue renting to build-up your down payment. Make sure you have enough $$ left in the bank to cover 3-6 months of your bills so that you can cover your living expenses in the event of another lay-off. This economy isn't turning around, so having a nest egg will serve you in the long run.
As for a pre-approval letter- they are typically only "good" for 90 days. We built our home seven years ago and I remember getting our preapproval about a month before the builder's estimated completion date only to go through the process again 4 months later because the pre-approval was no longer "valid". Each lender may be different, but you could look into a prequalification to see "what you can afford" at any time.