Important Note: This answer refers to RAMP stage 2 only - reusing your existing 5250 screens. It has nothing to do with RAMP stage 3 - replacing your 5250 screens with Visual LANSA components.   
It depends on the approach you use.
Imagine a simple 5250 application made up of four menus (or some other common access points) and 36 other screens like this:  
 

 

We recommend you use this approach:

1. Initially Perform a Rapid Navigation Modernization

In this example you would identify and define the four menus (or access points) A, B, C and D only, and snap them into RAMP as full screen destinations.

The entire 5250 application, with its modernized navigation, could now be deployed to your end users.

Normally you would also fully modernize at least some part of the application itself, to add more value to it.

At this stage answering the question "How long will it take to RAMP my application?" is easy: Allow 15 minutes per menu (or common access point).  So for this example, allow 4 x 15 minutes = 1 hour.

2. Now Perform Selective and Incremental Application Modernization

Now assess application areas A, B, C and D:

• How frequently are they used?

• Will full modernization increase end user productivity? How? What needs to be done?

• Will full modernization improve the end user experience? How? What needs to be done?

• Will full modernization aid the demonstration and marketing of your product? How? What needs to be done? 

Based on these assessments you might decide to:

• Modernize application area A and deliver it to your users as an initial release.

• Later modernize 60% of application area C and deliver it to your users as a new version.

• Not fully modernize application area D at all, because it does not add business value.   

• Finally, modernize 25% of application area B and deliver a final version to your users.

So answering the question "How long will it take to RAMP my application?" depends upon how you approach this step.

The question cannot be answered until you decide what parts need to be fully modernized, how much work needs to be done, and in what order.  

Key Points

• Navigation modernization is very rapid.

• Application modernization takes longer, but adds significantly more value.

• You can deliver a modernized 5250 application incrementally. You don't have to do it all in one go.

• You are not forced to fully modernize all of a 5250 application just to use it in RAMP.

• Some parts of an application may never be fully modernized before they are replaced with new Visual LANSA components instead.