I've been doing this some, thinking that segments will be an easier way for me to get to status than miles, and increase the chances of a bump.
I've been using
www.itasoftware.com.
Consider if I was looking for MSY-LAX, with as many stops on UA as possible. I might start with a normal search and note a baseline UA route. Imagine that my baseline (lowest cost) was MSY-ORD-LAX on the departure and the return.
and then start looking for longer routings by doing:
msy :: ua ua
lax :: ua ord ua
And then msy :: ua ua ua for 3 segments, and msy :: ua ua ua ua for 4. I'll come back to the return in a second.
The problem is that I think the ITA software engine hunts possibilities until it times out and then just presents the best of what it found. By the time you hit 4 segments, the realm of possibilities exceeds the time to explore all of them so I'm rarely successful with 4 or more initially. This is also why I locked the return into a specific routing of LAX-ORD-MSY based on my baseline fare. My initial searches are about exploring what I can do on the outbound flight initially and I want to hold the return constant since I'll come back to that later. The less time the engine spends looking at the return, the more time it can hunt for longer, cheaper routings on the departure.
I also pay attention to which airports are coming up consistently and inexpensively. Suppose that as I'm looking at 2 and 3 leg outbound flights, I notice that the best deals keep coming up as MSY-ORD. In that case, I might tell the engine that I want to explore options from MSY to LAX where ORD is the first stop. This means the processing time of exploring options via DEN or SFO can be ignored for the first leg and thus the engine will get deeper into 4 and 5 segment routes. In that case, I might try the following for a 4 segment outbound route where ord is the first stop.
msy :: ua ord ua ua ua
lax :: ua ord ua
Another useful directive is the + symbol. I can do the same search above but look for 4 or more segments with the following syntax:
msy :: ua ord ua ua ua+
lax :: ua ord ua
Another common example I've found is that I can see there's a segment inbound to my destination that's consistently coming up. Imagine that SFO-LAX keeps coming up as the last segment in my searches. Just as I locked in the first segment, I can easily lock in the last, such as this search for MSY-ORD-(unknown)-(unknown)-SFO-LAX, all on UA:
msy :: ua ord ua ua ua SFO ua
lax :: ua ord ua
Once I feel like I've exhausted the outbound options and found what I want, I reverse the process with the return. Imagine that I found the best I could do was MSY-ORD-DEN-SFO-LAX. I'd then update my "baseline" price and change my criteria to something like:
msy :: ua ord ua den ua sfo ua
lax :: ua ua
To look for 2 segment returns. Then 3, then 4. And so forth, especially focusing on the first and last segments just like I did on the departure.
I've begun to doubt the extent to which this is worth it over a pure mileage run. In playing around with this technique, I've found that I can generally tack on extra segments with Delta for ~$20 each. A couple months ago I did MSY-ATL-BWI-DTW-MKE-MSP. I got some more miles but I turned a normal 2-segment flight into 5.
My question, not yours, that I haven't thought much about is whether this is worth it, at least financially. Suppose that I could double my segments in a year from 30-60 by doing this. The 30 additional segments would be get me from silver to gold at a cost of ~$600. I could also fly another 25,000 miles for the same effect.
The question I suppose then is whether I could get 25,000 miles for $600. That's not impossible but not easy either (if it is, please shoot me some hints!). But it looks easier than all these extra segments, both finding them and flying them. I suppose that's why you don't see many people looking at maximizing segments. At the margin though, say if you were at 24 of 30 segments, and just wanted to get there, finding a 3-segment each-way trip could well be worth it.
By the way, while doing this, I discovered that the Delta kiosks couldn't print more than 3 boarding passes at a shot and they directed me to a ticketing agent. They seemed quite surprised by my 5 segment routing from MSY-MSP, offered that they could put me on something more direct. I just replied that there wouldn't be any adventure in that, took my 3 boarding passes and went on my way. In DTW, I was able to use a kiosk to print the remaining two and all went well.
Good luck!