How to handle hair longer than your arm's reach?

The culprit of hair knots are the split ends. Keep your split ends at minimum by moisturising your hair often and cut each and every split strand. Getting rid of split ends helps with detangling and minimising further damage.
Classic length is where your hair reaches right under your buttocks.
I lost that crown volume since my hair hit bcl. 

Since my hair reached tbl I decided to handle my hair like it was extremely long, even longer than classic, breakable due to age, dry because natural oils can't reach such a length (evtl. link from torin page with coconut oil), etc. So I gave my hair an extra TLC (tender, loving care).
Keep your hair moisturised
Dry hair is prone to breakage, it's fragile. Moisture keeps it manageable.
Some people can't handle sticky hair, hence why they don't use oils or use lightweight oils.

Condition your hair until it becomes limp and straight at the ends (not the same as limp on the roots though).
Don't force your hair to "make it behave"
It won't behave. You'll rip off your hair, you will have tones of split ends, your hair will frizz, but you won't make your hair "behave". Products make your hair even stickier.
Choose the updos that are most convenient for your hair at the moment. Sometimes your hair is dry because of heat in the air, some other times it's greasy even though you washed it yesterday. There are a lot of hair friendly updos (link to hair friendly hairstyles) for any situation.

Finger comb your hair prior to combing.

Check out for split ends.
Benign neglect
Up in a braid or bun and forget it. By this I don't mean that rats' nest of messy bun.

Comb your hair instead of brush it. Trust me, you'll have less hair breakage if you comb your hair instead of brushing it. Even super long haired on comb their hair instead of brushing it.Sveta Laduda and Ligeia Noire for example, not to mention indian women with thick long hair...

Keep in mind that not everybody can handle such lengths and it's ok to keep your hair shorter.