So say you join a band and for whatever reason one of the member's skill level is not at the same level as the rest of the band. I know "talent" is subjective but when someone simply can't perform at certain skill level it's pretty cut and dry. What would be an acceptable length of time for them to get it together before you have the "Sorry it's not gonna work out" speech. Also consider the person has been given ample chance to improve their skills but are either uninterested or incapable of getting better. This is also a full time working band and not a hobby or weekend band. Slightly related how far does loyalty go when it's holding the band back? Do you keep with what you have and let the band suffer or realize that it's a business too and find the best candidates for the position.