I am pleased to report that the birds appear to like their homemade suet

It really won't keep in the summer - I can tell it's a lot squishier than the commercial stuff! - so I definitely need to use it up this winter. I suppose I could put out very small nuggets of frozen suet in the spring as well, in the tray feeder. The birds gobble everything in the tray feeder by noon most days, so it'll probably still be frozen before the day warms up. Put some out for the window squirrels as well in the same fashion. Spring is when squirrels starve, their caches are all used up and new food isn't readily available*, so they'll appreciate a high-energy treat.

* though how true that is in a city is debateable!