Is it still worth building Shopify apps

I've been building Shopify apps for a couple of years now.
My apps, Pop Up Discount by MITS and Bulk Product Edit by MITS.
I'm wondering if this is a viable long-term business model.
Any advice or insights from experienced app developers would be greatly appreciated.
What kind of income should apps generate to continue developing them?

I forgot links
Bulk Product Edit by MITS - apps.shopify.com/bpe-by-mits
Pop Up Discount by MITS - apps.shopify.com/amax-popups-banners