Hi Can i continue to use mint 9 LTS after April next year
Yes, it won't stop working all of a sudden or anything.
You will stop receiving updates/upgrades though, and while you may be able to live with this on the application side, the lack of security updates is something to give serious consideration.
After a time, the Isadora repository itself will be closed (along with the Ubuntu 10.04 one), and you won't even be able to install packages via the normal method.
So you've got time, but start thinking about an upgrade path that makes you happy when the inevitable comes.
GIGABYTE GA-P35-DS3L LGA 775, Xeon 3.0 Ghz Core 2 Duo, 4 GB DDR2-800, EVGA 8800GT, WD Caviar 250 GB SATA-2
Ubuntu 12.04 LTS, Crunchbang Waldorf, Mint 13 w/Cinnamon, Elementary Luna Beta, Puppy