It really depends on the cartridge and how much capacitance it can tolerate. Grado cartridges can typically tolerate a lot more capacitance than others. Yes, getting a second preamp next to the tonearm and then running a long cable from its output makes sense if the preamp is of the quality you expect from your system.
I have a similar situation, about 13 feet of cable from tonearms to preamp. I bought a Stereophile Class C rated preamp, which was rather inexpensive, and put it on one tonearm leaving the other to deal with the 13 feet. Turns out the tonearm dealing with 13 feet sounded better than the one with the preamp.
So, I put the preamp on the other tonearm. The long run still sounded better than the preamp run. I wasn't expecting that result but it is what I got. Eventually, I will put a high quality preamp next to the turntable but for now, I am listening to 13 feet of coax and the Class C rated preamp is on the tonearm I use the least.
I have a similar situation, about 13 feet of cable from tonearms to preamp. I bought a Stereophile Class C rated preamp, which was rather inexpensive, and put it on one tonearm leaving the other to deal with the 13 feet. Turns out the tonearm dealing with 13 feet sounded better than the one with the preamp.
So, I put the preamp on the other tonearm. The long run still sounded better than the preamp run. I wasn't expecting that result but it is what I got. Eventually, I will put a high quality preamp next to the turntable but for now, I am listening to 13 feet of coax and the Class C rated preamp is on the tonearm I use the least.