Column with recycled sequence value

Hi,

suppose I have a let's say heavy used table. There's a column containing
UNIQUE in4
values. The data type musn't exceed 32-Bit. Since however the table is heavy
used 2^32 will be reached soon and then? There are far less than 4G-records
saved thus these values may be reused. How can this be accomplished?

I already defined a sequence but then?


I appreciate your help.