The "Time To Go" calculation is great to have as an indication. I like it although I would prefer it goes beyond 240h, but that is not what this feature request is about.
It is about, though, adding a similar but reversed calculation. Something like "Time To Charged", "Time To Full" or "Time to 100%" when charging to get an estimate of how long it will take to reach 100% with the amp input at the current moment.
This would mean a new dbus address, it could send out null when discharging and 0 when fully charged. I have no idea about the possibility or difficulty of doing this, so take it for what it is, a simple idea.