I really like this stuff but seems like it gets stiff after about month or so

There's so many types of Pline, which are you using?

Most line will gets stiff after a month or two of hard use. Try changing your line more often. I usually change mine once a week but even every 3-4 weeks isn't bad.

sorry guys its florucarbon

As said, I think any line gets stiffer after it has been on your reel for a month.  Elements like hard lake water, the sun, and heat dry it out.  Using a line conditioner will help protect it from the elements.