I do get why people with day jobs and small flocks would do this, and I'm glad to hear that it all worked out so well for you, Womble.
I have two concerns about sponging generally. One is the potential for masking reproductive issues - not really a big problem on the individual flock level, but given that a very large proportion of our rare breeds are kept by just such smallholders as Womble and Mrs Womble, it's a little frisson of a concern. But if it makes it easier for such folks to keep sheep, it's probably all to the good. I just hope enough breeders keep on doing it naturally, as well!
The other is about the ewe. Having read your blog, Womble, I'd suggest that please in future also use copious lube when
removing the sponge. If it's taking a lot of pulling out, like a not-full tampon as alluded to by Mrs Womble, then taking it out without lube could cause some slight damage