6 is my limit, anymore than that and some just end up sitting unused forever.

I have some made to measure Atama Gi's that I had custom fitted for me in Rio that are now 30 years old.
Which is kind of funny.
The jackets are still in good condition.
I'll probably be dead, and they will still be useful condition.
I do not regret their purchase, any more than I do buying good dress shoes.
As most of my real dress shoes (not necessarily the business casual ones) are also 30 years old, too, at this point.
Some things will outlive you, and remain in useful condition, if they are nominally taken care of and stored well.

I have no limit, but unfortunately the overly aggressive blue belts end up ripping them for me eventually. Always a sad moment, followed by the excitement of getting a new gi.

I agree with Tyler. I stubbornly refuse to set a limit on my number of gis. I hate it when they rip. It is always my favorite gis, because I wear them more often. I still miss my Jiu-jitsu Pro Gear gi. That was a sad day for me.