I'm still nursing along my 2011 MBP. It's my work truck. Everything in it has been replaced or upgraded, but it still works well. The point is that it was possible to upgrade it myself. I won't buy another Apple product unless it has that feature.
I was doing the same until last week, happily chugging along on my pet project when my 2011 15" MBP screen went white as a ghost. Diagnostics all point toward a problem with the GPU; apparently that generation has a known defect that's only (temporarily) repairable by replacing the logic board. A repair too costly for me to justify.
My recommendation would be to avoid graphically intense work if you hope to continue using the machine for a long time.
I was seriously bummed when my machine died. Fortunately I was able to buy one of the very last Apple refurbed 2015 MBPs, which is still user upgradable to some extent, and avoids all the horrendous design trade-offs of the more recent generations.
Oh, and no dongles necessary.