http://fixitfastelectronics.com/mfc9330cdw-9140cdn-emboss.ht...
The TLDR there is that the HL-3170CDW has a sharper-than-normal lift off angle from the fuser roller (the part that fails). Inexpensive toner is more sticky than the Brother-brand toner, so it causes undue fatigue on the part.
We had this same issue happen to us about 1000 pages after switching to an ultra-cheap, pour-in toner option. We first replaced the roller with a cheap one from Ebay that ended up causing the printer to overheat. Then we bought a custom manufactured roller from the aforementioned Australian company. That one has lasted us more than 3000 page so far, even with the cheap toner.
Note: if you elect to change the roller yourself, don't touch the heating element / bulb inside of the roller with your fingers!
The best printer decision I've ever made is my current printer, an HP OfficeJet 8620 with an ink subscription program. This HP has printed 9620 trouble-free pages since I purchased it a bit over two years ago (May, 2016). Yes, the per-page cost is relatively expensive, but it's the least hassle I've ever had with a printer. New ink just magically shows up in the mail shortly before I need it and I mail the old cartridges back for recycling. I haven't heard "honey/dad, the printer is broken/jammed/out-of-ink/won't-print again" since I purchased it.
My first printer was an Apple thermal printer, my second an Epson MX 100, so I've dealt with _a lot_ of printers over the years, from Apple, Epson, Canon, Brother, HP, and maybe other brands I'm forgetting.
I previously tried things like bulk ink tanks and refilling toner cartridges. Not worth the hassle.
I'm glad you're happy with your Brother. Mine had great initial reviews, but then when I checked back on Amazon a year later other folks has the same fuser roller issue:
https://www.amazon.com/gp/customer-reviews/R16HGOAIYLS1IJ/re...
Maybe it was specific to that model (HL-3170CDW). I don't know.