Question for moms of older kids (9+) re: bday parties

At what age do kids stop having a "themed' birthday party?  Many of the 5th & 6th graders I talk to tell me they have sleepover parties for their birthday, so I'm thinking age 10,11,12?  ds1 will be 9 soon and he's still attending/having parties that have some kind of a theme, so I'm curious.  TIA

From my experience it seems that around fifth grade or so it goes from birthdays parties to sleepover parties, but I guess I would talk to the child involved and see what they would prefer.

my almost 11 yr old still asks for a specific cake, but I stopped doing the whole party supply matchy thing a couple years ago.  probably because we do parites for 4 kids in 3 months.

Thanks hairmom & Sedona.  I was thinking this would be one of the last....I think I'm the only nutjob mom who loves to do themed parties.  It's a good thing I have a few more years with the younger two to continue my twisted obsession!