[x87678r]

That is a few extra days for one task. 6 months later you'll still be training the person, though the overhead will still be lower it still will be slower than doing it yourself. Then the person might leave and you start all over again.

[kqr]

This seems like the common mistake of trying to optimise for individual efficiency at the expense of the rest of the system.

Yes, overhead will be higher, but since capacity also will be higher, cycle time will go down much more (non-linear effect) and you'll extract important value and feedback out of the tasks sooner, easily paying for further capacity improvements.