As long as you keep all variables consistent, this shouldn’t be a problem. It is very important to maintain proper environmental control. Also, you should use a high quality dispensing system with repeatability specs that meet your needs (repeatability both in the xyz motion as well as in the dispensing itself). For example, if the dispenser is not giving you the same exact droplet size every time (or the same pressure and flow rate if we are dealing with a pneumatic syringe/needle system), then you can’t guarantee that your assays will be valid. I have seen systems that do not in fact give consistent dispensing results, so the researchers cannot get consistent data.