Sorry but for the cost of line I will usually replace it 2 or 3 times a year.
I use or have used various lines over the years, and the best for my purposes cost less than £20, in most cases £10.
Daiwa Sensor, which due to fishing near weed and snags would get changed every 3 months, the line was still good, but I would not take a chance after fish have taken me through lily beds and roots, which can be be covered in snails and mussels.
The same with Gardner Pro.
Both of those cost around £9.99.
If you want a casting line, then that would definitely get changed regularly, the force of a cast can be brutal on knots, even with shockleaders. I don't use an out and out casting line since Shimano Catana was taken off the market.
For my co-polymer fluoro coated hopefully low visibility line, I get a season out of them, but at around £20 a pop P-line Floroclear does not cast as well as more supple mono's.