I still feel even 5 is too many.
At one point I had around 15 at once (all in my signature inc 'gone' pretty much overlapped) and it was frankly ridiculous, but I did it because they were all synths I wanted to try out and find if I liked them, eventually when the novelty wore off, if they were not used enough or I didn't like them enough I sold them, and very glad I did as too many keyboards around me makes me feel slightly sick these days. I was basically living the 80s dream I had as a young kid when I couldn't even afford one proper synth never mind 20 but it wasn't exactly getting my music progressing any quicker.
A couple of my synths (JX-3P and D-50 in particular) are used on a lot of my stuff so are close to becoming part of my sound, I guess, but I also use lots of guitars/vocals so they are often just supporting - and D-50 is all custom/synth struct patches (not late 80s presets!).
I can't see me ever being without those 2 (sold and rebought D-50 cos the only sold synth I missed, sometimes the only way to know if you'll really miss/want it is to SELL it, not stick it in a cupboard as often suggested, that doesn't quite work the same if you have the safety net of knowing it's still around somewhere).
Sy77 and Polysix are 2 very nice keyboards I can't seem to let go, SY77 goes for so little it's not even worth selling, and non full velocity transmit aside it makes a great master keyboard for me (esp for Piano parts - VST pianos not onboard samples!). And Polysix/101 give me that proper analog mojo which I occasionally need in my more synthetic tracks.
I could find myself happy with JUST a jupiter 8 and maybe a digital of some sorts (D-50 would prob be my choice there) so I think you have the right idea.
) cost so much more . 
