Is it okay to ask for a letter of recommendation more than a year before applying to a master's program?
Explain this situation to each of the few professors you plan to ask for letters of recommendation from, and ask what they would prefer. Some of them would probably prefer to write you the letters now, while you are fresh in their memory. Others, (ones who are very well disposed to you, or very generous people) might like to wait until you are applying for specific programs, because then they can tailor their responses to the specifics of what you are applying to. Even in that situation, you will feel less awkward if you have already broached the topic with them. Also, you learn if someone you are expecting a recommendation from is actually not willing to write one for you, or feels that they can't recommend you strongly. This will be better to find out now than a year from now. 

Plus, your professors might have advice on what kind of job to take in the meantime in your field, or even a connection for a job. You won't know if you don't ask.