The general format for most Maiden solos is as such:
Adrian is the ONLY one who usually keeps the majority of solos in tact for more than 3 years after the album with the song has been out. He shows by far the greatest amount of live technical accuracy and consistancy. Parts are changed, but they are changed from the studio versions and then kept the same from show to show. Many of H's solos today are still very very similar to the originals from years back. Ex. "The Trooper", "The Evil That Men Do", etc.
Dave will usually play a solo very accurately for maybe a tour or two, and then it just starts to become a lot of improv, but like Adrian it shows some degree of consistancy over time. Though on the most recent tour he has shown a lot of improvement and regaining the accuracy of some of his older solos. For years Dave has been playing a live version of "The Trooper" solo that is very different from the record, yet very consistantly the same all the time.
Janick usually completely alters his solos live (arguably because he doesn't even write them in the studio, just improvises them on the recordings), and from tour to tour they will completely change. Listen to his solo on "Brave New World" on Rock in Rio and then Death on the Road to see what I mean. One melody is maintained because it's really simple and catchy, the rest is just totally altered.