I've been doing this for a good while, too, mostly off samples. Herecy, some would say; nothing to lose, I say. I have considered Billy's point about possible chemical reactions, but so far so good on that front. The only downside is that the blend tends to go softer than its constituent parts, possibly simply from the stirring.
Rather than a 'mixed' label on the container, I go with names. Current ones are Fougere Fusion (classic and fougere types, including LPL, SDM), Italian Stallion (Italian barbershop, including SMN, ADP and Nuavia), A Very Ventus Soap (a few Aventus dupes plus a spray or two of the fragrance itself), and Bitches Brew (truly a brew; various Grandstaffs, B&M Seville, Myrkvidr, ...). Four in number, in other words.
*Damn, I should be offering my services as a brand and name consultant.