Some key aspects for defining stability in a CHF patient: 
The absence of congestion, and therefore orphopnea, and edema
No recent weight increases
Adequate cardiac output at rest
Systolic BP of >= 80mmHg and pulse pressure of >=25%
The ability to dress without stopping and to walk a city block
Psychologically sound - some patients, such as those with serious depression may require psychiatric consultation.
35. Grady KL, Dracup K, Kennedy G, Moser DK, Piano M, Stevenson LW, Young JB. Team Management of Patients with Heart Failure: A statemetn for healthcare professionals from the cardiovascular nursing council of the American Heart Association. Curculation 2000;102:2443-2456.