More questions about extents

Having established the next extent size for a table (thanks group) I tried to reduce this by alter table modify next extent. I then updated stats on that table, but still the next extent size is showing as large as ever (oncheck -pT shows 360000) Looking at systables the next extent size is the original next extent setting (10000). I realise I need to re-organise the table and re-establish extent sizes but is there any way I can stop it gobbling up chunk space in the short term? Thanks. Phil.