Back in January 2006 when I purchased my first Festools (TS55 and CT22) I paid attention to the advice of my dealer, Jesse Berragan of Eagle Tool, Los Angeles.
We had known each other many years. He knew the first thing I do when breaking down a sheet of plywood is to make a clean-up cut along one long edge. He also knew I did not own a truck and that my "shop" was in my second-floor condo. Although Jesse mentioned the benefits of a 2700mm or 3000mm guide rail, his advice was that neither was practical for me at that time.
What he did recommend was that I buy 2 extra 1400mm rails and use the coupling bars in the accessory kit to connect those. This way, I still had a single 1400mm rail for cross grain cuts without disassembling my long rail. Yet when I needed to go on location, I had no trouble transporting the 1400mm rails. When the time came to connect them, the third rail served as the straight edge.
A few weeks after I showed my TS55 and CT22 to a good friend, he bought his own TS55 and a CT33, plus one extra rail. For years we would work together building projects. Since he had turned his 2 car garage into a shop, he had space to store a long rail. I bought a 3000mm rail which I kept there. In 2009 I found that in my condo I could use a 2700mm rail so long as I was careful. I ordered that to be delivered.
When I bought my TS75 it came with a 1900mm rail. With a TS75 to rip 8' material you really need the 3000mm rail, or you need to couple a 1900mm and 1400mm rail.
Since I built my shop in 2010, all my rails are kept there. For me working on-site is now the exception. For those times, I keep 3x1400mm rails together. Yes, my new truck can even transport our 5000mm rail, but my experience is it is easier on most sites to put together a couple of rails rather than lug and maneuver a long one.