For a long time, a 2013 i7 CPU with 32 GiB RAM running LTSP over ESXi was more than enough for intensive use of 5 thin clients.
We've recently switched to a more powerful server (refurbished 48 AMD cores / 256 GB RAM) running Proxmox and despite some issues that still needs minor tweaking, I am very happy with it.
The only gray area, and the reason I am always looking for alternatives to LTSP (NX2Go is the strongest candidate), is the huge bandwidth used by LTSP: 8 Thin clients needs a sustained 600 Mbps. I'm afraid scaling over 10 / 15 workstations will require expensive network equipment but graphic user experience is near native in all aspects.
I highly recommend to anyone that is in doubt of using LTSP or any other thin client setup in production, give it a try because it actually worth it in all aspects.