Credit score changes, in general, do not change that much over time. Your credit score is calculated each time it is requested;. This can be a lender request or by you. Each time your credit score is calculated it takes into consideration the information that is on your credit report at that time. As the the information on your credit report changes, your credit score can also change.
There can be delays by your creditors in reporting information to the credit bureaus. Also, the type of changes in information will affect your credit score. For example, opening a new credit card account will be more significant a change than simply having paid your bills on time the previous month. Also, something dramatic like a bankruptcy judgement will have a significant impact in the calculation of your credit score.