We are running an outdated version of Civicrm (4.2.7) on Drupal 7 and working on upgrading to the newest version of Civi, 4.6x. We have been quoted a full forty hours by a consulting company for the completion of the project, but as the database is designed to be upgraded, this seems excessive.
If you have experience in upgrades and could offer thoughts on how long it should take as well as likelihood of errors, it will greatly help our planning. We have some custom fields, including some forms directly linked with our website, but not an excessive amount.
Thanks!