I don't think there's any ideal mix- it's entirely project and environment dependent. A couple examples:

###All Experienced It might be appropriate to have all experienced team members on a critical project with a tight deadline, where there's no room for junior developers to get up to speed.

###All Junior In another example, it might be appropriate to have all Junior developers in a more R&D oriented project. There was a team at one company I worked at made up entirely of interns to whom projects that needed an innovative (but not necessarily fast or correct) solution were assigned. They were real customer problems, but they didn't have any known good solution, so they got interns who would be new and have few preconceived notions.

The point here is not that either of these approaches is often right- more that projects will run the entire gamut between them based on business needs, organizational factors, and the availability of developers.

I don't think there's any ideal mix- it's entirely project and environment dependent. A couple examples:

All Experienced

It might be appropriate to have all experienced team members on a critical project with a tight deadline, where there's no room for junior developers to get up to speed.

All Junior

In another example, it might be appropriate to have all Junior developers in a more R&D oriented project. There was a team at one company I worked at made up entirely of interns to whom projects that needed an innovative (but not necessarily fast or correct) solution were assigned. They were real customer problems, but they didn't have any known good solution, so they got interns who would be new and have few preconceived notions.

The point here is not that either of these approaches is often right- more that projects will run the entire gamut between them based on business needs, organizational factors, and the availability of developers.

I don't think there's any ideal mix- it's entirely project and environment dependent. For example:

It might be appropriate to have all experienced team members on a critical project with a tight deadline, where there's no room for junior developers to get up to speed.

In another example, it might be appropriate to have all Junior developers in a more R&D oriented project. There was a team at one company I worked at made up entirely of interns to whom projects that needed an innovative (but not necessarily fast or correct) solution were assigned. They were real customer problems, but they didn't have any known good solution, so they got interns who would be new and have few preconceived notions.

The point here is not that either of these approaches is often right- more that projects will run the entire gamut between them based on business needs, organizational factors, and the availability of developers.

I don't think there's any ideal mix- it's entirely project and environment dependent. A couple examples:

###All Experienced It might be appropriate to have all experienced team members on a critical project with a tight deadline, where there's no room for junior developers to get up to speed.

###All Junior In another example, it might be appropriate to have all Junior developers in a more R&D oriented project. There was a team at one company I worked at made up entirely of interns to whom projects that needed an innovative (but not necessarily fast or correct) solution were assigned. They were real customer problems, but they didn't have any known good solution, so they got interns who would be new and have few preconceived notions.

The point here is not that either of these approaches is often right- more that projects will run the entire gamut between them based on business needs, organizational factors, and the availability of developers.