Re: longevity and sustainability
I run a calligraphy studio out of my home and yes, you can earn a decent salary doing calligraphy but you will probably never get rich.
When I first started out, I was pleased if I could do 35 sets in a day but after doing this full time for three years, I can regularly do 75 sets per day and have done 90 in a marathon session. In other words, you get faster and more accurate as you go along.
With that comes pain and discomfort, as you've already discovered. I have arthritis in my hands and I've had to have custom ergonomical pens made--that has saved my business. I've also just finished my first round of physical therapy--8 weeks of physical rehab which has helped tremendously! I learned exercises for neck and back, ergonomics, hand exercises, prevention and pain management and it's worked wonders. I wish I had pursued it three years ago when I first went full time--it would have saved a lot of pain and misery.
As for getting work year round: I do work all year round but there are ebbs and flows. January through September is very busy with March, April, and May being the busiest. Things slow down a bit around the end of Sept. but then pick up again in late November through New Years then the cycle starts again. It works for me because I love the fall and I enjoy a break that time of year.
Wedding work is steady and reliable but I've learned that I need to pick up corporate work as well for financial reasons as well as creative reasons. It's fun to have a challenging assignment amidst all the envelopes and place cards.
If you love lettering and you would be looking for every minute to devote to picking up the pen anyway, then maybe starting a business is for you. The work can be repetitive and solitary but doing what you love, being your own boss, and working from home has its charms.
Lastly, I'll be honest. I'm married and we have my husband's income, too; if we depended on my work alone, my calligraphy business (at least at this point) would not cover all the bills.
Good luck and let me know if I can help in any way.