According to WikiP the current 7 day WR is 1546 miles. Assuming this is accurate, is there not a fairly reasonable chance of this being broken by one of the current riders?
Seven days
On Sunday 17 March 1940 Pat Hawkins, an 18 year old female from Western Australia, set the 'World Seven Days record' in Perth, having ridden 1,546.8 miles (2,489.3 km) to surpass the previous best (1,438.4 miles (2,314.9 km)) set by Mrs Valda [or Ada Vera] Unthank of Hastings, Victoria. Hawkins also broke the West Australian records for one, two, three, four, five, six and seven days, plus surpassing the Australian professional men's record of Ossie Nicholson.[39][40]