How to Add Display Blanking to Single Digit Nixie Clock (PIC16F84A ASM Code)

I recently built this Single Digit Nixie Clock.
http://www.electronixandmore.com/nixieclocks/3.html
I’m not new to electronics but must confess that I know very little when it comes to programming only dabbling in Picaxe’s and Arduino’s. I was so taken by this little clock I even got round to having a pcb made for it. The only drawback I could find was that there is no option to blank the display when not being viewed and so prolonging the tube. It could be incorporated within the code and fixed as I don’t really need it to be changeable with menus. I've looked at the asm file but I'm finding it hard work.
If anyone could help I would greatly appreciate it.

Without source code changes are possible, but difficult.
Maybe you can use a hardware solution?
You can simply disconnect the power from the lamp,
with direct switch or timer circuit.

Thank you for your prompt reply. I've also been told that the code could be changed to load the hours register in the main loop and compare against the blanking time period that's desired to determine when to skip the display call routine. I was hoping that with some help a blanking option would then make the clock a very worthwhile project. I have designed and had manufactured a number of professionally made PCBs and using an IN-12 with socket and LED backlighting it's also very attractive. The whole idea was to give them as presents to the family. I think it would probably be a good idea to offer one for services rendered as I know very little when it comes to writing code and I was not aware what was involved.