Yes we did a 12 month rtw backpacking trip when we first retired at 62 yrs old.
and a
4 month round the world
and a
4 month Europe only
and many more long distance travel.
Visas (this is a minefield so make sure you read the requirements for each country, Russia China and India have certain restrictions, if you don't feel confident yourself sorting Visa out go through an agent, insurance, inoculations, malaria tablets (which can be very expensive). Ask your GP they will tell you what you need.
Which way round the world to travel, base this on climate and weather conditions.
First decide how long you will be away for, break it down into which countries you would like to visit and the cities/areas within those countries and days spent in each place.
Mode of transport, flights, ( there are round the world tickets which allow a certain mileage although with some air alliances you can add miles on. Cruise ship, ferries, trains, hire cars, coaches. or a mix of all these.
Accommodation, hotels,hostels,self catering, camping, camper van, boats etc.
What to take, what not to take.
Decide on a budget
I took 2 years to plan our first trip it does take time
Good planning can be the difference between an amazing trip and a disappointment.
Some people do wing it but what I would advice after a long flight pre book accommodation for at least the first night because you will be very tired and the last thing you'll want to do is start looking round for accommodation.
In our travels we have covered the USA coast to coast twice, Canada coast to coast, Caribbean islands, South America, Pacific Ocean islands, NZ, Australia Twice, Galapagos Islands, India, Maldives, Hong Kong, China, Thailand, Cambodia, Sri Lanka, Russia, 4 months Europe including the Scandinavian countries, 4 months travelling in a truck in Africa Cape Town to Kenya. The Canaries Islands. The Holy Land, Egypt, Dubai, Jordan.
To get the most out of the trip allow at least 2 nights accommodation one full day site seeing. One night stop overs are hard.
The good thing about planning your own itinerary is you can stay in any place as long or as little as it suits you.
Advice if you are using agents double check you are getting what you want. Even the big companies make mistakes and don't forget they charge you for their services.
Have a great time.