Stihl 440s, 400c, 460s, 660s, 880s... Huskies 268s 372xps/xts 365s, 385, 390, 394, 395s go quick. Some saws don't need much, tighten the squish, slight flow changes and minor duration changes and they run pretty darn well. IMO based off of my a little over 2yrs worth of porting/machining, I can rip out a saw in 4 to 6 hours... (providing I've done them before)... if its a saw I've never touched... I'm studying it, a bit curious and cautious... but, once it go time, its essentially the same as any other saw...
The 2 saws that take me a little bit are the 461s and the 500i/660 hybrids... I'm into those saws for about 6-7hrs... the 461s, I trench the case and match it to the cylinder so extra precaution is needed as i dont split the case.... the 500i/660 hybrids get a bit of machine work... mainly on the piston crown, then opening up the inside for the small end of the rod, clearancing the stuffer sides, (more towards the rear 'corners' of the stuffer)... some saws, depending on the build complexity and saw design call for more time... but, I'm certain y'all have done countless amounts of saws. And With that, you all know what works and what needs to be done to those specific saws/cylinders. So in theory... if you ported the same saw chassis 30 times, the 30th saw should be faster than the 1st time you ported it....and it should faster than the twenty-fifth time you ported that same chassis...
When I first started porting, I used hog a lot of material out of the ports... sbit man, i created A LOT more work than what was necessary. I've found in a lot of cases, less is more... example: when i build the 500i/660 hybrids, I run 106* - 108* on the exhaust. I try to limit the 4 stroking while keeping it in the peak torque range... these saws still hold solid rpms, but you can actually lean on it and flex the *s-word out of it, even with the upgraded suspension...
Some guys cut with grace and allow the saw to do its thing, while other guys like to power cut and push it... the guys I build for, they like to push it so I've strayed away from the high rpms.
Y'all who have been doing it for years know the truth... push comes to shove, you know what works, you know what has to be done, you've honed your skills, you have the tools that make the work easier and faster, the only thing taking time is the motivation to get the saws done faster.
That's my honest take on it.