patching the liner a lot

Last spring I spent a couple of months finding leaks in my liner and
patching them. Each leak involved raising the water, waiting a few days for
the leak to lower the level, then gentle inspecting the perimeter of the new
water level to find the leak (pond is 8x15 so the perimeter is long),
lowering the water to get some room to work, patch leak, start over.

At what point should I give up and replace the liner?

I'm wondering if starting over again with concrete would be a better long
term solution. How think would I have to make the concrete on a pond this
size?

Can anyone recommend a pond consultant (I live in the Boston area), I could
hire / talk with?

Thanks. I love my pond...during the moments when I'm not fixing it :-)

Brian