The only real investment would be the batteries. Depending on the use, they can last from 1.5 years (if discharged totally on a daily basis) and up to 5 years (if the batteries are bigger and they are only discharged at under 50%). But this means that you have to buy more expensive batteries in the first place. Deep Cycle Batteries are meant for deep discharge and as the research stacks up in this field, they will be better and better. This means that by the time you need to change your battery for the first time, the expected lifespan of the next will already be significantly higher than now.
The inverter should be changed every 5 years, but in this DIY system's idea of making it scalable, the system would run on parallelized inverters, which could increase the maintenance to up to 10 years or more.
Contrary to the biases in the industry, the cells are not affected greatly by the passing of time, provided that the glass is not scratched or does not mattify over time. This can easily be resolved by either investing in a pressurized solar panel washing system on the roof or by polishing or changing the glass every 5-7 years. I choose the latter.
http://energyinformative.org/lifespan-solar-panels/
It seems that it is a good time to invest in solar energy. The first step is the hardest :)
And the changing of one's habits to consume less, that's even harder.
Changing the habit is though. This is something people are not ready to do (and me the first). We are however trying, at our scale, to do small things. Integrated over time and people, small things can yield something bigger.
Concerning solar panel, I will try one day for sure. But for now, I have no time. It is great you manage to do all you do. I am not capable of :)
I hate delegating responsibility, most of the time the quality of the work being done is just bad, and not because I am subjective or picky, but because nobody puts heart in your project but yourself. I am doing half-made things usually.
I am not sure this is better than just doing one good thing.
Cannot really judge here ;)