if you but a good quality braid it can be on your reel for a few years. i know people whove had the same braid on for 4 years.
mono might only last a few weeks on your reel.
so while braid might seem expencive initially it can actually work out cheaper in the long term.
dont get into the trap of thinking of using braid for everything all the time. i carry reels with braid and mono on and only use the braid if i feel the conditions and ground suit it.