There should be no need to turn your heater on or off all the time. If the heater has a thermastat it will do it automatically - (like at night when the temp drops a little, it will come on). It should be set on around 26 degress celsius or about 79 Fahrenheit.
If you have plants in your aquarium, the lights should be on for 8 to 10 hrs a day to promote healthy growth.
If you have no plants, then 6 to 8 hours a day should be fine.
When you upgrade your tanks you will need to cycle them.
The easiest way to do this is by setting it all up - so put in water, heater, filter ect and let in run. You can add some Seachem Stability (or something similar) once a day for 7 days or until you get a Nitrate reading. Then you can introduce your fish to their new home. Try to get the old and new tank reading about the same PH and temperature to help reduce stress.
The way it works is that ammonia turns into nitrite and then nitrite turns into nitrate.
Ammonia and nitrite are very toxic to fish and will put them under a lot of stress.
The only way to get rid of ammonia and nitrite is to do water changes and if you do change the water youll have to add some more healthy bacteria (eg seachem stabilty) to the new water, or pour it straight into your filter.
So you will also have to buy yourself a test kit so that you can check your tank for these things.
Im not sure either how to tell the age of bettas, but apparently when they develop a "hump back" they are a little older.
Goodluck and Im sure your bettas will enjoy their new homes