I have a six-man shop. An eight-year employee is asking for 3 weeks of vacation next year. What would you do? What about sick pay? He is a valuable employee, $15.00/hr plus limited benefits.
After an employee has been with me for 1 year I give them two weeks paid vacation/sick/personal days. They can use it as they see fit. Plus, all employees get at least 7 paid holidays off. If I had a valuable employee that had stuck around for as long as your guy, I would give him the three weeks. In fact, I would probably have done it sooner--maybe after 4 or 5 years. I guess the question in your case is what are you giving your other guys? If you give him three weeks will it cause a problem with the rest of your crew? I've found that it's a good idea to have a standard policy regarding stuff like this so there is no question in anyone's mind as to what they will get and when.
Good employees are tough to find, as are good bosses. I only have 1 employee. I treat him well and he treats me well in return. I pay him over $25 per hour plus the medical benefits he wants, no sick leave or holidays or vacation, and he earns it. We worked this out when he started and I didn't have benefits in place like we do now, and we stick to it.
If you raise your prices in your future bids by $.50 per hour you will have enough to cover the expenses for him. And you probably won't lose any jobs, because say you have a job with 100 hours labor = $50.00 their cost. 6 men X 2000 hours per year average = 12,000.00 hours X $.50 per hour = $6,000.00 per year, which is a bit more than what the cost of $15.00 per hour X 40 hours equals (works out to $600.00 per year). That should be enough to cover the costs noted in the above posts and you will be fine, as long as he is worth it.
I raised my shop rates by $2.00 per hour recently to cover unknown expenses like insurance increases, which I think are likely soon, and nobody has noticed it. Jobs come in the same as always.
That is not true in California. When you get your annual audit, you are required to pay the workers comp on vacation time. The reason is that otherwise, employers could call a large portion of the time paid for "vacation pay" and reduce their workers comp costs. The workers comp people want you to pay on bonuses, vacation, holiday, even gifts to employees.
I would however make certain that there is a notification period of at least 60 days for any vacation time of over 1 week duration and 30 days for 1 week. This way you can at least make plans for that time when he is gone.