I like to take sample buds at many different intervals, especially with new strains. You must dry and cure properly, however. Be as scientific as you can and you will have great information at your disposal for the next time you grow that plant. Like, hey, this one was great when cut at 9 weeks. Or, waiting another week on this plant made it taste worse.
I take a small bud, mark the date, dry and cure properly, and do a full report when it's ready to smoke. Sometimes I've found that I like certain strains a little bit early as compared to others. It's all personal preference and you should do whatever you need to learn more about the plant you are growing. No one will kill you for taking a sample bud. Just don't quick dry it!