How to automatically go to the next level

Like games such as Cookie Clicker, the save time for Clicker Heroes is usually around 30 seconds to a minute.

According to Reddit, this game can be found around the web at various places, such as its website, Kongregate and Miniclip and that each version has differences, such as the Steam version does not have a login feature.

But, upon experimentation, the game autosaves approximately every 60 seconds since its launch.

As said in this answer, you can avoid having to wait up to 60 seconds for the autosave to occur (since your last action) is to hit the wrench at the top right corner and then 'save'.

I don't believe there is any difference between the treasure chest spawn rate depending on what level you're on. It's a base 1% whether you're on level 100 or 1000%. Source

A maxed Dora will give you a +1000% percent chance of a treasure chest spawn; which works out to roughly 1 out of every 9 (or 11%).

Relics would also give you a boosted chance to get a treasure chest spawn; but I highly doubt it's per level. If it was; I'd think that eventually you'd hit a point where every monster is a treasure chest; and that would probably break game balance.