I agree with *most* of what you said - but used a different approach when I started my 5 string adventure... Because I was playing in several bands, some of which would never need a 5er, I learned the songs that required a 5er on one, but played most of the "4 string songs" on one of those... I still use the same approach, and bring one of each to gigs that call for it - that way, I always have some sort of a backup(although I've never needed it)... This accomplished a couple things - I think it sped up my learning curve on the 5er for the songs I needed it for, and still allowed me a "breather" while on the 4s - since I find them easier to play, even to this day... That way, everything I play sounds like it's supposed to... I've averaged 100+ gigs per year for over a decade - and am on pace to play around 130 this year, so I must be doing something right...