My 11 year old lab, Hazel, has a brain tumor. To start she had 7 seizures in 24 hours.?

this was in July and it is now November. The phenobarbital is at 90 mg, and she is doing Ok She has only had a break-thru 2 times. Her motor skills (front leg mostly) are a bit challenged now, & she is starting to have a weak bladder. She is also ravenous and thirsty all the time (snuck a pecan pie, a bag of brown sugar the other day, along with 4 bananas) Otherwise she doesnt seem to be suffering.She will still chase a ball any time u ask. It is difficult to know it may be over soon, and we are uncertain what to expect next. There seems to be no information on brain tumors and their progression, plus we are not even sure she has one. It is just surmised from her age and symptoms. Some say we will know when its time to put her to sleep, but I am just not sure, with our emotions in the way, that we will know the right time. Any suggestions? resources? Thanks.