Eric,
It might be useful to use the script that I mentioned earlier with the one-second intervals, then graph the seconds column against the first memory column and maybe you'll see some big spikes.
I will get onto it as soon as I get a chance, I promise.
The one-minute intervals look somewhat suspicious simply judging by the steady climb to 300+MB. This might be justified, depending on what you're drawing.
I was pushing it a little this time with gradients and 2 blurred clones. Still, compared to the stuff I see done with Inkscape it's really not that extreme. I would send it to you but I see the filesize is 1.9Mb (due to a logo with text to curves). I'll try chop it down and get a working example that I can share.
Below it is in minutes and KB. It only drops once at 20:24, which is when you mentioned noticing slowness.
Your log doesn't doesn't mention opening files. Is this all from one drawing?
I opened an existing drawing to start and at one point I drag/dropped an svg (the logo) into the drawing.
I'll log more carefully next time too.
Thanks for the info, Donn.