WARNING: some databases have not been vacuumed in 1953945422 transactions

Hello,

we are using PostgreSQL 8.0.3 and have two databases in one cluster. db1 and db2.
Each night a shell script is being executed.

vacuumdb --analyze -U cmduser db1
vacuumdb --analyze -U cmduser db2

The last weeks the following warnings are given out:
WARNING: some databases have not been vacuumed in 1953945422 transactions
HINT: Better vacuum them within 193538225 transactions, or you may have a wraparound failure.

Now I made the sql-statement:
SELECT datname, age(datfrozenxid) FROM pg_database;

Yesterday I got this result:
datname age
db1 1.090.080.531
db2 1.940.858.511
template1 1.940.858.511
template0 1.940.858.511

Today I got the following result:
datname age
db1 1.075.558.667
db2 1.075.513.031
template1 1.955.716.521
template0 1.955.716.521

Why are there changes of the databases template1 and template0 ?!?

Is this critical?

Regards
Michaela