Learning magic is a perpetual process, it's not stopping and starting over again.
We find a cache of bits we like to do and slowly we begin to replace certain routines with newer effects or handlings that interest us and help us "improve" upon or otherwise change how we are perceived as entertainers. About the only time I've seen or done a cut and move to new move usually stems from creating a completely new act, usually a seasonal program or something special such as a Patriotic or Religiously themed show (as examples) that are performed certain times of the year for specific events or groups.
The only other major exception I've seen (and encourage) is when one is shifting away from traditional magic and into Mentalism and maybe Escapes in that "real" escape work is not the same as doing Illusions designed to look like an escape, it's a very different world.
It's perfectly normal to have two or three complete acts at the ready; material that's polished and which can be rotated as you get repeat clients. Keep records as to which act you brought to that group when and when they call you back bring in a different set so as to allow for a sense of variety. I used to work a "Blackstonesque" family show from early spring through August and then shift into my Macabre show for about 12 weeks a year and then an end of year holiday show run that took up about 6 weeks of the year. Other than special promotional bits for business clients, that was pretty much it.
Not certain if this fits the sort of goal you're shooting for, but it's what I know and understand as being "normal" in the biz.
BTW. . . if you aren't bored and sick & tired of your act after 3-6 weeks of constant rehearsal, you're doing it wrong. To work a set act you must know everything about it better than you know the back of your own hand. This is why many of we old guys encourage your youngsters to build a stage act and take it to the Theme Parks for a season or work the Carney circuit. If you do an act 5+ times a day for the 16 or so weeks of the typical season, you'll be able to make some solid impressions.