You can amend/make a new Will as many times as you want. It is important to keep your Will updated at all times. If you do not update your Will after major life events, it may not reflect your wishes under new circumstances. Typically, you must consider making necessary changes to the Will after major life events e.g. marriage, divorce, childbirth, change of mind about legal heirs, acquisition or disposition of assets, change of Executor, death of named Beneficiaries, etc. When you make a new Will it will render all previous Wills null and void.
Aside from these major life events, it is advisable to review your Will once a year and make any changes you deem necessary.