Need more sleep

I am only averaging about five hours of sleep a night and that is with taking a sleeping pill.
I go to sleep about 10:00 without a sleeping pill. I can fall asleep quickly but around midnight I wake up and I'm wired.
I take a 10mg ambien and that gives me and extra three hours of sleep and I get up at three in the morning.
I have tried other sleeping pills with the same result.
I do not drink coffee after 10:00 in the morning.
I am 78 years old!
Anyone have any suggestions on how to extend my sleep.
I use a res med 10 air sense auto with a Fisher and Paykel Simplus mask.
I never have any air leaks

Have you tried going to sleep later than 10? Body clocks can change with age, regardless of OSA and Cpap. It may be unnatural to start so early now, especially if Cpap is working for you.

I am so tired from lack of sleep that I can only hang in until 10:00. Sometime I doze sooner!

Have you tried just not taking the Ambien for a few nights (in case the effects hang over for a couple)?

Have you been checked for other problems with labwork, etc. recently?

Do you nap during the day otherwise, using Cpap?

Can you try Sleepyhead software to see what's going on overnight (all info and posting instructions are here)?

https://sleep.tnet.com/resources/sleepyhead

https://sleep.tnet.com/resources/sleepyhead'/sorganize (and the 's' belongs).

Sleep maintenance insomnia (that's where you can't stay asleep vs sleep onset insomnia where you can't fall asleep at bedtime onset) is a tough beast to tame because it's really hard to figure out what is feeding him much less make him go away.

Do you take any medications? If so what are they?

Do you have any idea what might cause the wake up to start with...pain, bed comfort, anything external?

Have you verified with cpap software that your cpap therapy is optimal and nothing there could be part of the reason you can't continue to sleep to your satisfaction. If not, start there with something that is fairly easy to see and fix and we have to start somewhere.
See if anything is just screaming out "fix me and you will sleep better".

Google "sleep maintenance insomnia"...lots of reading on the subject and tons of potential culprits of which sleep apnea is but just one.

Wrong again - do not go to bed until you are sleepy. Lying in a bed awake id poor sleep hygiene.

ALso studies are showing that your need for sleep does not decrease as you age, but getting sufficient sleep is more challenging as you tend to wake more.