Hi there, my best advice would be to plan the time, if you genuinely enjoy her company and not just the sexy time. it could be fun just chatting with her or watching some television with for a bit. Also it wouldn't hurt to ask her what she had in mind for the 4 hours. You could also get a takeaway. If I was planning the time I would chat, warm up, sex, eat something (takeaway), warm up more sex, watch a bit of tv or something, warm up again, more sex and then take a bath together. However if you don't enjoy her company I wouldn't bother with 4 hours.