How many years can one sleep in 2-3hr intervals, up to 6hrs total/nite, before signific health risk? Even with occas nurse help, sleep is same (trachs

Forever? It is very likely that some people are naturally "biphasic" sleepers, meaning that they naturally sleep best in two separate segments. History shows that humans largely slept this way until the advent of electricity, and some cultures still sleep this way. My advice is to listen to your body. Whichever type of sleep you function best off of is the best for you.
Depends. While the most commonly cited number of hours of sleep needed for healthy body functioning is 7-8 hours of sleep, it truly depends on what age group you are in. As you get older, your sleep cycle changes with duration of rem vs non-rem (rapid eye movement) sleep change. As you enter your senior years, you may need less sleep and often find your sleep interrupted. This is normal.