In my humble opinion shaking too vigorously or too many times exposes the nicotine to more air than required and will promote degradation.
Well, in mixed
juice which isn't usually ment to last long, + you reopen and refils from countless times, then in my view it doesn't matter, but respect your opinion of course.
I feel the same as you with regards to nicbases from sources which I trust have a proper blended base sent to me, in which case I don't even shake or mix it at all afterwards - It doesn't fall out of solution unless 60+C, and I usually buy nicselect nic from vendors who don't dilute themselves but gets big batches of nicbase prediluted and batchtested by alchem themselves(well, outsourced pharma-subcontractor, but regardless), and e.g. in such cases I never shake/mix the base afterwards, only in premixed juices from that base. Well, I wouldn't shake/mix nicbases from most reputable sources anyways, as I think they are blending the product themselves properly.