I was hoping to finally see an advanced time filter so I could do something like "over 2 minutes" but it seems you've only got the same ones Youtube has (< 4 minutes, 4-20, and > 20).
If it's an opaqueness restriction with the API or something, I'd like to suggest letting us at least combine the provided ones, so I could do something like (4-20) && (> 20) to get "over 4 minutes" which doesn't exist on Youtube but seems pretty useful.
Another thing that would be useful is filter-by-channel since the search function within Youtube for searching a channel's uploads (using the search button on a channel's page) is a significantly nerfed version of their usual search function.
I wish I could select "between 2.5 and 6 minutes". That search can translate to 2 queries to YouTube (<4 and 4-20), then the results can be combined and pruned to keep only those between 2.5 and 6. To get enough videos if there aren't enough after pruning, we could access the 2nd, 3rd and so on pages from the results. But I doubt YouTube will like 6 searches in a row.
Yea and I'm doubtful we'll see a service willing to do their own post-processing per-query while also being at the whim of Youtube's API (official or not).
Ultimately, I would like these features to come to Youtube itself since there's a lot of nice features built into it that would be hard for a third-party to replicate without permission (such as playing videos inline on hover, with captions).
I doubt it will ever happen. This is Google after all, not a small company we can hope will get it right after a while. They've left the search parameters shitty for years. Google, arguably the most advanced search company ever, can't make an efficient filter for custom time ranges? They obviously can, but, as other comments have noted, they seem to think that good search is an anti-feature.
I looked into youtube's search filters recently, and the length range option is stored as an enum (stored as base64-encoded protobuf in the sp query parameter), so it doesn't look like it's possible to set to specific values.