I would use the internal (unbalanced) charging system only when in a bind.
When you use protected cells theoretically you should be fine, however I feel the individual cell protection should be a last line of defense an not used on a regular basis.
I have a lithium battery pack for a rc-car where one of the cell exhibits a significantly higher self-discharge rate.
Using a balanced charger the pack works absolutely fine, however if I were to charge it unblanced results would most likely be catastrophic.
While this is not 100% applicable here (no individual cell protection, cheaper quality) it highly discourages myself from handling any lithium rechargeables carelessly.
Although it is probably already careless enough to be still using this particular pack...