Long term travel can be difficult because of stay restrictions in most countries. For example, the Schengen area of the EU allows a maximum of 90 days at which point you have to leave. If you are planning to move around within the Schengen, there is a handy Shengen calculator that helps keep track of your stay there to avoid overstaying your allowed visit time.
The EU is implementing, what is essentially a digital ID for foreign visa-free travellers in the Schengen Zone known as ETIAS, which stands for European Travel Information and Authorization System. From their website:
It is a completely electronic system that allows and keeps track of visitors from countries who do not need a visa to enter the Schengen Zone....
The legal procedures to pass the ETIAS have started in 2016, and the system is expected to be fully operational in November 2023.
The ETIAS is not yet implemented (as of August, 2022). The EU travel website will post updates on the program and when it will be in operation.
Another handy website is Sherpa which provides information on travel requirements for your destination depending on the passport you hold.
Here is a good video of a couple who travelled in Europe for a year. They detail how to avoid the visitation restrictions in the various areas of the EU. This primarily involves moving within the EU but going in and out of the Schengen area.
