In Lightroom 3 if you trash all the old backup folders is it going to effect the your catalog in any way? there are 61 backup folders in my lr catalog 61 seems redundant . It eats up a lot of space "162.91 GB on disk ". And yes I optimize my cat regularly.
To answer the question simply, each catalog LR creates is independently valid, so deleting a backup lrcat file will not impact the original from which it was created.
However, the fact that 61 backup folders total 162.91 GB on disk seems suspicious. That would be an average size of 2.5 GB. Is your primary lrcat file (not the Previews.lrdata folder/package next to it) in that ballpark? I'm guessing it'd be somewhat larger, since the backups have probably been getting bigger as the catalog grows (and the average is brought down by the earlier, smaller ones).
I ask because for all the catalogs I've seen, only a small handful are over 2 GB. One reason for the backups folder to be that big is that you've accidentally opened one of them and started using it so that it has built up a large preview cache.
If that's the case it explain the size, and it'd make that the advice of deleting them all be a bad data loss mistake.