How rapidly does a star's absolute magnitude change by goes through a rapid change in luminosity?

A Sun-like star goes through a rapid luminosity change between stages 8 and 9, when the luminosity increases by about a factor of 100 in 10^5 years. On average, how rapidly does the star's absolute magnitude change, in magnitudes per year? Does this change would be noticeable in a distant star within our lifetime?|||Many stars are variable in brightness for intrinsic reasons (activity within the star as opposed to eclipsing binaries). Cataclysmic variables, such as SS Cygni and U Geminorum, can increase in brightness by four or five magnitudes ( a hundredfold brightness change) in a matter of hours, and do so every few weeks. At those times you can actually see the star visibly brighten with the naked eye. That's one of the reasons I'm hooked on observing variable stars!