What's funny is I've probably ridden (avid motorcycle/adventure tourer) most every road and many of the trails west of the MS at least once or twice in the past 25 years, so I thought I'd mix it up a bit in an airplane by doing a cool X-country and flying over/following some of my most favorite and scenic rides. I've done many 1000-3000 mile loops and just thought it would be kinda of cool to condense one of my favorite loops into a couple days of flying. No biggie though... there's a couple real nice sunrise to sunset loops here in AZ that I could knock out in a few hours of flying that would cover pretty much all extremes.
while my long CC was longer than most, and involved a flight across the cascade range, I'll say that I was pretty tired after 4 hours of flying. the altitude tired me out and the flight happened at the end of a nervous day of preparing/briefing/thinking about the flight.
i revised some personal limits after that flight to include using oxygen if i'm sustained over 12,000 feet for more than an hour or so and to set a soft limit of 4 hours. I may extend them later, but I'll tell you that was plenty for me, and it was on a beautiful day with a lot of it in sparse area where my workload was pretty low. my short CC were much more intense, as it was all in busy airspace with lots of special airspace, traffic, etc to manage/avoid.
if your instructor agrees, I think perhaps a longer solo CC can be valuable, but I do think you're talking about a full trip. I think the benefit would be, late in your primary training, to PLAN that trip, and do a ground review with you CFI, with the goal not to go fly it, but to see what you might have overlooked, what special airspace would you have mistakenly blown through, what TFR did you miss? Does your fuel stop have fuel, is it NOTAMed to be closed the time you at ether, if the pump doesn't work, how close is the next place with fuel? does the alternate have stuff you need to know? (left hand traffic pattern, weird tower hours, diagonal runways, terrain in the maneuvering path, a fly in that day that will mak eit a metal cloud of death for a student pilot? etc). I am a fan of planning long trips, like you want to take post PPL, but you don't necessarily want to fly them all, you want to plan them, and then get them critiqued to see what you might need to add to your planning
good luck on your training adventure, I really do hope you go through with training, but be willing to learn something on every flight, even after you have your PPL