There’s lots of good advice here.
I completed Chase the Sun a while back, 205 miles from sunrise to sunset, and I’m sure there’s other threads with this title.
My suggestion would be to include a century once a month . The TR plans are great but you really need to get used to spending 5+ hours in the saddle.
You’re already doing 40 miles so start building that up pretty quickly.
I followed a Gran Fondo plan (I think) and tried different gels and drinks etc.
Enjoy yourself 