How long is the Wall? - There is often some confusion here between ‘The Wall' and ‘The National Trail', as they are not the same thing - hence there are two answers.
The Wall (as built by the Romans) was 73 miles in length, running between Maia (Bowness-on-Solway) and Segedunum (Wallsend). In the present day, existence of the stone Wall is mainly evident over approximately a 30-mile stretch, between Birdoswald and Chollerford. Beyond those two points, the line of the Wall is generally identifiable by the ditch (the Fosse) that was in front of it, or the mounds and ditch that lay behind it (the Vallum).
The National Trail is the long-distance Path that runs between Bowness-on-Solway and Wallsend. Where practical the Trail follows the line of the original Wall - diversions having been added in certain sections to make it more appealing (eg a footpath along a riverbank rather than through a modern busy city centre). The length of the Trail, at 84 miles, is longer than the original Wall.
What is the Hadrian's Wall Path? - It is the full name given to the long-distance National Trail, which is adjacent to parts of the Roman Wall, created and maintained by the Countryside Agency, in partnership with numerous other agencies - including English Heritage, the National Trust and Northumberland National Park.
How long is the National Trail? - The entire Trail is 84 miles long. Some folk walk all of it, some part of it and some choose to take diversionary routes off it in order to take in sites of interest like Vindolanda and Corstopitum.
When does the Trail close? - It doesn't, it's open 365 days of the year. The Trail isn't promoted outside of the main season (April - October) as too heavy a footfall during the winter months can lead to worn paths on the grassy areas becoming boggy in wet conditions. Individuals and small groups (four or less) isn't a problem at any time, however larger groups are generally encouraged to stick to the summer months when it's easier for the ground to be seeded and maintained.
Where is the Best of the Wall? - The answer to this is entirely subjective, however it is a commonly used term that is applied to where you find the stone Wall is most prominent and the landscape is particularly breathtaking. With those two considerations in mind, the ‘Best of the Wall' is generally regarded as being the 30 miles stretch in the central section between the Irthing and North Tyne valleys. That said, there is much to appreciate either side of the central area, it's just that the landscape is different and the visible heritage is not predominently Roman.