I think treating it as a job where 75% of the salary is experience is probably the right attitude. FWIW I worked with a lot of grad students and anecdotally saw the best outcomes from people who within 2-3 months of showing up knew exactly what they wanted to do, were in the lab 10-8 to do it, graduated in 4-5 years and immediately got top-tier jobs.

I knew people who spent (7, 8, 9, 10, 11) years as a PhD student and they sure didn't seem happy or end up particularly good places...