Hello
I have over 28 years extensive experience with Filemaker Pro and have developed, deployed and maintained many instances from very large and complex down through to small more simple deployments, including with v5.5, which is getting on in age quite a bit now!
There are a number of advantages to migrating to the newer versions of FMP, I will just need to get some additional details about the project, including which version you are considering moving to (the latest version is v16) and structural details on the current database solution you have.
If you would like to contact me, we can confirm a plan and I can provide a more accurate timeline for completion.
Thank you
Darren