Ive got just £100 worth .
Ive had them for about 15 (maybe more) years. In that time Ive won? £25!
What Ive read online etc though, seems to suggest, that the more you have ...the more chance you have of winning.!
My neighbour (now deceased) had quite a lot (Im not sure how many), and he seemed to win something pretty often.
As you say, the interest rates these days are naff.........so probably worth a punt!