Depending on how aggressive your play is, a good set of flats or wounds will last a long time. In the realm of 1 to 2 years for rounds, and over 5 with flats. Kudos on the BB424x. I have a BB424x with chromes. The BB also sounds great with rounds and depending on how much you play or how aggressive your style is, strings should last at least 2 years with regular usage. If you're considering flats, let your rounds get into the muddy sound and wear they down until they break, and buy strings in bulk as an investment.