I NEVER do FREE assessments, ever. My time is more valuable than that. I charge the full session rate for an assessment. I do offer a free consultation, but that is only 15-30 min long and a comprehensive assessment can take as long as 90 minutes without the questionnaire.
I used to offer all sorts of free things; assessments, basic program design, consultation, etc.. That was before I realized that my time and my worth as a trainer is more than a free value. Be careful with free offerings because it says something about the way you value yourself as a trainer.
As far as assessments go they are absolutely necessary for programming and also for motivation and client retention. Depending on who I am training and what the goal is I can do an assessment every week, every 3 weeks, every 6 weeks, or every 3 months. It really depends on the training system I am using.
If I am training a strength athlete and I run a westside barbell training methodology then every week there is an assessment for upper and lower body. If I am doing a block type periodization for an athlete then it can be every 3 -4 weeks or every 3 months. If I am working with a fat loss client then it can be performance testing every 6 – 12 weeks. It depends on the goals of the program and type of client.
The bottom line is clients need to see results and know that they are getting something for what they are paying for and you need to see if your program is working effectively, so testing is never a waste of time.