Wonder what your thoughts are on this. I think the purge process should be every year, and an ongoing part of business. The other option is the shock and awe of a mass purge.
There is no third option BTW, every company lays off just as every company hires. The pain cannot be avoided; it's rather the frequency and scale of that pain.
So, I would maintain it should be every year. Part of the reason this layoff is so daunting is because full rigor was left out of the focal process. It's a pay me now or pay me later thing. Best to have an annual purge that is borne of rigor, than to skip over the hard stuff and deal with catastrophe later.