I'm really new to
vaping but I unless there is huge flavor distance like say from menthol reds to sweet strawberry or something drastic like that I don't bother cleaning.
For instance I was smoking a vanilla caramel and just refilled with a caramel. After a couple of puffs the vanilla just went away so probably not worth the effort.
If you are trying different vendors/flavors in small size bottles to determine if you want to buy bigger bottle I'd maybe lean towards cleaning it so you can get a true test of the flavor. I've found I like caramel and vanilla quite a bit but not so much for the tobacco flavors as they never tasted like a real cig to me. What I've been doing with the sample bottles of the tobacco flavor is mixing them 1/3 tobacco flavor and 2/3 with the flavors I like so I don't waste the sample flavor samples I don't care for. So you really don't have to clean unless you are looking for a true flavor taste and not have any old flavor left behind.
Looks like you got the 12ml bottles from the picture. My samples that I have been trying are from 3-5ml bottle size until I figure out what I like.
Good luck with your vaping experience.