How long does sperm live?

My husband and I had sex this morning at around 9:30am. I hadn't noticed any significant CM throughout the day (but then again, I chalked discharge off to left over semen). Tonight at 11pm I noticed I have heavy ewcm (probably the best ewcm I've documented) but my husband is asleep. Is there hope that the sperm is still alive in there and benefiting from the cm? I know that healthy sperm can live at least 72 hours, but does that go down if the sperm count is lower? My husband had a low count but has been taking supplements to boost it. Thanks for any insight!