I leave my tea bags on for much longer, two months plus. I have been using them for about four years with no problem, ad they keep the weeds down too. Nothing grows under them.

Leung wrote:

Clicio, according to Ryan Neal, the teabags which in your case is 4-5 weeks old, should not be removed.

m5eageoff, Leung.
As much as I respect Ryan and Mirai Bonsai videos, and I surely enjoy his teaching, I think there is always different ways of doing the same things in bonsai, with good results.
To point out my experience, I was leaving the teabags for two to three months, but the fertiliser inside (BioGold) was simply disappearing after some weeks, and leaving the plant with no nutrition. So I shortened the time to what Bjorn recommends HERE , and it is working alright up to now.
Perhaps it is because of the temperature or heavy watering, or both here in Brazil.
Please take some 1 or 2 minutes to see this information below:

Video-Bonsai Empire

And keep posting your experiences!