Clutch Master Cylinder Problem?

[Hammer]

I've been losing clutch fluid recently and since I've replaced the slave already (and there isn't any leaking noticable there) I am thinking the master cylinder is need of replacement.

What's the latest on replacing these. I was looking at the Autozone Duralast lineup, reasonable pricing but thought I'd see what experience anybody has with them, if any.

Any other recommendations on this job?

Thanks in advance folks.