More training, better planning, and staying in shape over the winter are all reasons to be pleased.
Getting on the subject of Heart Rate though and the question of using that as a proxy for improvements is something I find dubious at best.
Quite frankly, if someone asked me to help them plan their training regimen and didn't have a power meter, I'd strongly urge them to use RPE.
Probably the easiest way to test your fitness is using a similar approach one that Alex Simmons posted in an article. Basically time yourself up a climb of a known length (say something that is in the 20-40 minute range) and compare your performance to past results.
Heart rate has a tremendous amount of variation and the factors that go into that variation are numerous. Yet for the many factors that may go into an elevated or slower heart rate, many of them do not in the least compromise performance.
Here's another example of how HR deceives: pedal backwards, with one leg even on your bike while stationary. Do it fast enough and your heart will be racing and even reach max if you can hold out long enough. Another example, go on a gym circuit where they have those arm-pumping/circling machines. Have at it as fast as possible and watch how your heart will race. Yet in both cases, high heart rate is not correlating with high cardiac output. Not to mention heart rate both lags in response to effort but then it also drifts over time on longer efforts.
All HR does is give you a bit of information about the stroke volume of your heart. None of which is going to help you truly go faster on a bike, power & how much work you do - those help you go faster.
By the way, there is no evidence that bradycardia (low resting heart rate) is at all indicative of fitness. Some sedentary people even will naturally have this condition.
Back to the HRM issue, I would go so far as to say that for the most part, monitoring HR is only going to give you an extra layer of data that only serves to complicate the training process. Take some time to learn about RPE and what values are associated with which training zones & adaptations. Basically then train as needed in the right zones, for a sensible frequency/duration, and the positive adaptations will come.
If someone forced me to train w/o a PM, I'd then train exclusively by RPE. The best riders in the history of the sport all trained by simple RPE long before the flood of gadgets came during the late 80's and 90's.
As is, RPE modulates power training (as I do it at least) already. The two go hand in hand.
Added bonus, RPE is priced right and freely available