How do theorists in STEM fields update equipment? As a theorist my chief capital costs are software and computers (for large calculations and simulations). If starting at a new institution I would ask for these in my start up budget (about 20k USD). But in 5 years these items might all be obsolete and incompatible. What do I do then?

I understand that most schools have computer replacement programs every x years but the type of computers I would be asking for in start-up are quite expensive and not your typical campus machine. 

I am curious what other theorists have done. Especially interested in those that might be at a primarily undergraduate institution.
I'm not at an undergraduate institution, but I am a theorist in a department that doesn't have many of them.

My summation of my startup costs were "People and computers".

A couple of things to potentially consider:


People. Support for a programmer, or a grad student, or undergraduate salary for the summer.
Consider negotiating for a recurring or longer term startup package. For example, my startup doesn't expire. I know someone else at another university who negotiated for "A workstation costing $X,XXX, replaced every 5 years".
Data costs. If you use data sets, or could conceive of using data sets that cost money, you want to allocate startup to those.
Similarly, travel and publication costs.


Another approach is to ask your Chair if the Department needs something, and put that in your startup in exchange for...favors, or unallocated funding, etc.