Combinations - Safe times to take Valium (Diazepam)?

[ironmics]

So swim took two 5mg valiums yesterday(he's prescribed 3 a day for muscle spasms) about 8 hours later and not feeling any effects he decided to drink about 5 glasses of wine, thinking the valium shouldn't affect his system anymore. SWIM found out the hard way that this was an absolute terrible thing to do, blacked out, and was hung over for most of the day. The valium is very nice for his back pain but isn't absolutely necessary due to scripts of percocet and tylenol 3. If he took a 5mg of percocet and 5 mg of valium tonight without drinking would he be ok or would the 10mg from yesterday still be floating around to fuck him up?