sequence / last_value problem

Hello List,
i did this:
1. dumped out the schema of a table from pgsql7.1.3  (i had to modify it
a bit) and inserted the schema in pgsql7.2.1
The table has a id - field of type serial. (it is the primary key)
The field 'last_value' of the corresponding sequence has the value '1'.
2. dumped out the data of that table from pgsql7.1.3 and inserted the
data in pgsql7.2.1

The field 'last_value' of the corresponding sequence has still the value
'1' (the table contains now ~2 000 000 rows).

Is the reason for this that i didnt't call since now the last_value? Is
this normal and correct behaviour? Do i have to set 'last_value'
manually with setval? Does this mean that when i insert a row not using
the default value of the sequence,  i have to update 'last_value' of the
sequence every time manually? Am i missing something?

Regards
Tina