Just a quick little question.

Is the reward repeatable at the start of every month or from a month after you did the last one?

For instance, if i did troll invasion and got the reward on the 31st of september, cause i then do it the next day on the 1st of october and recieve another exp reward?

Thus being similar to how peng points work (every wednesday it is reset).

yes you can, I did it like that a couple weeks ago.

Okay thanks for the reply,

also what day does tears of guthix reset?

Tears of Guthix resets one week after the last time you do it. So if you do it on Thursday 4pm, it resets again on Thursday 4pm next week. And also, to be able to do it again, you have to gain 100k exp in that week or 1 quest point.