I have a 20" bmx a 24" bmx and a 26" dirt jumper all are single speed.
over the last year I have really started to like going on epic all day rides
and I think this is a direction I want to explore. I have done rides as long as 60 miles and I want to go much much farther.

I need a bike more suited to this type of rideing, something with more than one gear and geometry I will like after 100 miles. my dj frame with a 400mm seatpost is not exacly the best setup. I want something that I can ride on road off road and even way off trail. I want something I could ride to my sisters house self supported 1600 miles away next spring. I don't know if I want a hardtail or a little bit of rear travel with a lockout.

I am 31 years old 5'11" 230 lbs and I ride about 14-16 hours a week

when it comes to budget I know 1 thing, LIGHT, STRONG, CHEAP pick any two!!!
I will spend whatever it takes.
my goal is reliable, consistant, and durable weight is secondary
It doesn't have to weigh 20lbs as long as it isnt 50lbs

I am only looking for suggestions at this point and will consider any options given
I have a bmx background so I don't know where to start looking, there is so much avalible in the mtb world.

I know it will end up being a custom build but it can start as a complete that I upgrade or as a bare frame build

I know I am asking for alot.
please give me a little guidance
thank you in advance