Keep your spirits high.
While I will send LOTS of vibes for your hubby to remain Leukemia free, if he does not, you have good reason to be positive minded about it. Im sure you know lots about HCL, but for those who dont, broken cells ("hairy" cells) in the bone marrow build up making it more difficult for the bone marrow to produce various types of blood cells (RBCs, WBCs, and platelets, aside: if his RBC and platelet numbers are normal, and no "hairy cells" were found on the CBC its more likely that hubby has an infection or something else, and your Doc is just being extra careful because of the history. 3 is not a frightening low count so be positive!). Even if the HCL returns after a period of remission (which is VERY common, many physicians and scientists consider it "incurable" or chronic) it is one of (if not THE) the most treatable and best prognosis forms of leukemia. To my knowledge, treatment is usually necessary only when symptoms actually interfere with everyday life, and about 10% of people just "live with it" never requiring any treatment. Those who do, can begin with purine analog therapy, (eg pentostatin) which has much milder side effects than chemotherapy. If your hubby previously responded to treatment, he should respond equally as well to the same treatment re-administered. If unresponsive to purine analogues, immunotherapy (like interferon alpha) usually produces great responses in patients with HCL.
With continued monitoring, and treatment when necessary, your hubby should have a normal or close to normal lifespan.