AFAIK, the only units that Garmin no longer supports with Lifetime Maps are the really old ones, like the GPSMap 276. I have never seen a post complaining that updates have been discontinued for any Nuvi. We have a member over at GPSReview who has complained that they will not honor his lifetime subscription for his 276. That is about the only thread I've seen on the subject across multiple sites.
http://forums.gpsreview.net/discussion/comment/198851They have slowed the pace of introducing new Nuvi models however. If you are really concerned, you can choose a recent model here. Note the links on the left for 2015, 2014 and 2013 models:
https://buy.garmin.com/en-US/US/cOnTheRoad-cAutomotive-p1.htmlAs a mapmaker, I suggest that you look at the glass screen models like the 35xx series. They do much more precise map rendering than other Nuvis that I've seen. They treat the map like a 3d model and give realistic 3d views that you can rotate, tilt, pan and zoom with simple gestures in the map browser.
I am very impressed with their rendering, will post some screenshots when I get back to my PC (writing this on my MacBook Air now). They offer some interesting possibilities for mapmaking. They also include a special map, gmapdem.img that includes DEM data for all of North America. When you enable it along with a map (any map), it will be wrapped around the 3d terrain.
GPSCity (maybe other vendors) have had the Nuvi 3590 and 3580 factory refurbs in stock from time to time for really low prices. I like these because they are from the 2012 model year. That was the only year they offered the custom dashboard feature. I wrote a detailed tutorial about creating your own dashboards, and it allows you complete control over what is displayed on the main map screen.
http://www.gpsreview.net/creating-custom-dashboards-for-your-nuvi/I have a Nuvi 3550 which works with these. Mostly I use a Dezl 760 though because I like the big 7" screen. It is resistive, so no multi-touch. But the software is almost identical to the 35x0 series. It has the same 3d map browser but does not include the gmapdem.img file and cannot do 3d terrain. It will do DEM shading if you use a Garmin map that includes it, like the topo products. However when you switch to 3d view, the map isn't "wrapped around" the terrain. I see refurbs of these for $225 at GPSCity.
If you like to use custom routes, then I would suggest you stick with the 2014 and 2015 models however. The old "trip planner" prior to those years has been the subject of many complaints. Trips are not like routes, they are more like a collection of start and stop points. So the device will only display the distance to the next via in your custom route and not the final destination.
I gather that Garmin finally addressed these complaints in 2014 and made the trip planner more like the traditional route planner. Have never used on myself, and rarely create custom routes so it's not really an issue for me.