I have 3 for winter use, 2 for summer, and 2 "bars" that probably could be used anytime of the year. But I'll be buying two more to help set me up for NB18.. Thus, I don't know how to answer the question. .
You obviously want to buy more soaps, but why? If you just want to try a bunch of different soaps, then why not get a bunch of samples? You don't need an entire cake of soap just to try it out. You can get many more soaps for the money with samples, and store a lot more soaps in a given space. So do you need more soaps? If you have at least one cake of shaving soap and it is not nearly used up, the answer would be no.
Trips that are: A.) farther than 150 miles from your primary residence, and B.) not repeated more than once every six months, are considered "special events". As such, items purchased during these special events are considered souvenirs, and will be billed against the vacation budget. Most importantly, purchases will be executed without regard of need, want, or storage space. Hope this helps.
As long as you have one that works well, yoou have what you need. After that it is stuff you want. As long as you can afford it, that's fine.
I only started wet shaving in Feb '16 and already I have 65 soaps and am loving every one of them. You can never have too many.