One danger of going too slow is that you start to forget material that was burned. It is good to go at one’s own pace, but going at a pace where it will take 7 years to go through the material is far too long. There has to be a middle ground, and to be successful it will require you to push yourself a bit.
The early level material is more important than the later level material, I think there is some benefit to going through the first 25 levels at a pretty decent pace (no more than 2 weeks/level), then slow it down. I completed 27 levels in my first year, but ultimately took 3.5 years to reach 60. The slow down was partially to keep a reasonable workload, but mostly due to leeches. Be mindful about keeping leeches under control - this crept up on me before I realized what was happening and ultimately I ended up powering my way through only to deal with a huge mess now.