Can I switch from a Split Trust to a Split Trust+30 and vice versa?
No. Once the plan is under trust it is irrevocable. You cannot therefore switch between the trusts at some point in the future. If you think that the clients may want to change their mind over the survivor being able to access the benefits you may want to consider writing a separate plan for each person and use the split trust. The trustees are not then restricted in who they can give the benefits to and can choose whether or not to give the benefits to the survivor depending on their needs at the time.