This should not be a problem as your default route (primary) will determine which peer ip address becomes active.

since you are using 8.2 version the above configuration will not suffice as this will only work on 8.4 upward can u post ur current nat configuration

Do you mean static nat you could have this on your asa 1 nat (inside,outside) source static 10.10.10.150 10.10.10.150 destination static 20.20.20.50 20.20.20.50 asa 2 nat (inside,outside) source static 20.20.20.50 20.20.20.50 destination static 10....