CHF is how my Chelsea left me. She was on Vetmedin for less than a year (I don't remember when she went on it) after I knew about the heart. Near the end, she went onto 2 meds for her heart, and 2 diuretic medications to try to reduce the fluid buildup as her organs were shutting down.
How long she'd had it, I can't say, I think it was caught late in her case. She was an active dog her entire life, seemingly endless energy. Fact is, at 11 1/2yrs, she had more energy, spunk, than April did when she was 4. April will walk up one hill I can think of, at the same speed Chelsea did just a month before she died. She really slowed down though her final few months. But, the spirit doesn't leave. The day she died, out on the lawn, she picked up her head, and ran. Not hard, not far, but she ran. I was beside her to catch her for the inevitible Syncope episode.
I know this doesn't help, but enjoy your time remaining. Make more good times, I hope you have many. And, very importantly, take lots of pics of those times.