Good question. It seems kinda short to me.
We prefer a 60 year search for purchases and minimally a 40 year search for refinances.
Well, think about the life expectancy of a person who might raise a claim. If you've examined the title back 60 years and resolved any clouds that might reasonably affect title, the likelihood of a party with a claim coming forward is remote.
There are circumstances in which it is prudent to search back even further. If you have a substantial commercial transaction with concerns about rights of way, you may wish to go further back. In cases where the proposed insured are concerned with mineral rights, a special mineral search is necessary and that typically goes back as far as deemed necessary to cover likely conveyances.
Trust me. Experienced professional title examiners have no respect for title insurers who cut corners and do short searches. They are sacrificing quality for search cost and believe me, the reduced cost of the search is not likely to be enjoyed by the consumer.