It shouldn’t matter, no. Whether you’ve been at the company for 2 months or 20 years, you should be given an equal opportunity to meet expectations and succeed within your role.
The reality is that that does not always happen. If you have not been with the company long, your employer unfortunately may be short-sighted, and may think that it would be less of a headache to simply let you go than to spend any time or money trying to restore the employment relationship. Likewise, if you have been with the company for decades and are ‘old friends’ with the owners and managers, you may be used to them turning a blind eye to any bending of the rules.
Employers should be treating every employee equally, and that means an equal application of discipline. A new employee should be given a proper opportunity to succeed, just as a longer-term employee in the same role should be held to the same standards.
It is also important to note that courts will be more skeptical of performance concerns when they relate to a long-term employee with a good record. After all, it is hard to explain how a good employee suddenly becomes so bad that discipline or dismissal is warranted.