Retainer Negotiation Question

I recently did a PC>Mac + Exchange migration for a 20 seat client. We discussed an upfront monthly maintenance retainer of 30 hours at $125/hour (reduced from my hourly of $150/hr.)

In trying to finalize the retainer, they are asking for any unused hours to be rolled over to the boss’ personal computer needs (I service his family at $150/hour). Once this “spillover” is depleted, then the amount goes up to $150 again.

To me, this isn’t what I signed up for and it seems shitty, but I am wondering if anyone else has had to deal with this and how you deal with unused hours in a retainer.

I would tell them to take a hike but times are tough!