Reid Brothers Plumbing & Heating

Our 2-stage furnace started to blow only cold air in November, 2013, when the weather turned cold. Reid Brothers was called and they came December 5, as promised. The technician and assistant were courteous and asked to come in through the back door and took their shoes off without being asked. The technician explained that the furnace failed to turn on after 3 tries (the warning red light blinked twice every few seconds), so the fan would come on and stay on even though no heat was generated.
He said the cause might be a dirty flame rod. He cleaned the flame rod. We told him about the absence of of sound from the condensation drain. He then found a leak on the condensation hose and clamped it. The furnace then operated normally, only requiring occasional power off/on to re-try lighting the flame. We were billed, before-tax, $66 for this "Travel & Diagnostic" (regular $73.00, a discount of $7.00 was granted based on "Total Home Comfort Agreement Savings).
Our furnace was serviced September 16, 2013 at a charge of $152 (before tax). Would it be fair to assume that the service (including cleaning blower, burner, flame rod, etc.) could keep the furnace running normally for more than 2 months? It required service again in early December as explained above.
My suggestion to homeowners is to ask about warranty periods on annual maintenance services, and to ask about service call charges (it is fair to have to pay for travelling and diagnostic).