If Alpha Skip Ahead is currently on build 1910, how long would it usually take for beta...

I'm in the Preview Program and in Alpha Skip Ahead Ring, I'm testing several 1910 builds but at the moment no new UI for me.

Are you on Alpha? 1910 got releaesd so it should update fine now

https://news.xbox.com/en-us/2019/06/01/june-1st-new-preview-alpha-skip-ahead-ring-1910-update-1910-190530-1940/

Is your console enrolled in the Xbox Insider Preview Program?

In May they have issued a fix for video corruption on Netflix and YouTube for Alpha Skip Ahead
insiders. This should find it's way in the next update coming in June, if there are no new issues with that fix.

Alpha skip ahead I'm currently in beta just think it would be cool to be able to help at the cutting edge of new development

There is only a limited number of free slots in Alpha/Alpha Skip Ahead.

If someone in Alpha/Alpha Skip Ahead leaves, or is removed due to inactivity, participants in Beta are invited to Alpha. However, Beta participant invitations are sent out to those, that leave valuable feedback, find bugs, and are most active in the beta
group.

So it's not how long you are in the program, but how valuable your input and bug reporting was in the past.

Added to the fact that invitations are only sent out if there is new room in Alpha, you might have to wait a while to get invited. Just provide good feedback and be patient.