For any medium or large company, the $200-ish cost of a commercial wildcard certificate is a non problem. I think let's encrypt is mostly useful for small businesses and individuals, who can live with these limits.
This where LE is for me different from usual cert providers.
It's not really that hard. I manage a dozen+ certs manually, I get reminder emails 30 days before they expire, and it takes literally a few minutes to submit a new CSR. I could autmate it even more than I do, but https://xkcd.com/1205/
Currently (today, 21 February 2018) the limit is 39 months, starting 1 March 2018 the limit becomes 825 days. These limits are set down in the Baseline Requirements, which are rules agreed between the Certificate Authorities and Browser vendors (in practice mostly OS vendors) at their standing meeting. Chrome at least actually implements these in software, ie leaf certificates which seem to have a longer lifetime are simply invalid and don't work.
In practice commercial CAs tend to sell products as 1 year, 2 year or 3 year, and then they use the extra days in the BRs to let you "keep" the extra days if you renew early, so that you don't feel the need to wait until the last minute to renew to get maximum value.