The only time it is ever appropriate to invite yourself over to a date’s place for a sleepover is if you’ve had way too many tequila sunrises and should not be operating a motor vehicle. Then, and only then, do you have permission to ask if it’s OK to crash on their couch.
If they say no, call a cab. If they say yes, they better get you a nice blanket, some pillows and definitely not try any funny business (you’re drunk, remember?). Otherwise, like any proper lady, it’s customary to wait for an invitation.
By inviting yourself over, it makes you look kind of desperate and, in not so many words, you’re pretty much saying, “Let’s have sex tonight!” When you finally get that long-awaited request for the pleasure of your company, keep in mind the morning-after etiquette.
A sleepover doesn’t equal marriage. Be aware of how your date’s acting and if there is a leisurely breakfast in your near future or if they are trying to kick you out, so they can get to work. Either way, good luck!