kibblewhite valves

[kfx400rider03]

im replacing my stock valves they keep stretching.
i was thinking of going tih kibble white valves they are cheap for just the valves but do i realy need the valve spring kit? cause that is a little pricie. could i use my stock valve spring?

[Springbok]

Did you use the Whitekibble valves? Do they last longer??