I think they're great; fantastic value and you don't have to worry about using them sparingly. I test everyday from CD10.
I got a positive on my internet cheapie on CD12 but negative on the clearblue digital. On CD13 the internet cheapie was still positive and the clearblue turned positive- so this was the main surge day. The internet strips are way more sensitive at 20mIU/mL, the shop bought ones are usually 40mIU/mL.The best times to test are between 10am-3pm, then 5-10pm, with optimum times at 12pm and then 8pm. Some surges don't last long so it might be an idea to test 2x a day at 12pm and then 8pm otherwise you might miss it. You can afford to do this with the internet strips!
I liked catching my surge on the way up with the internet cheapies and then confirming it with clearblue so I knew in advance that I was entering my fertile window. Unlike the SMEP instructions, I test everyday from my first positive until it turns negative. Ov occurs 6-48 hours after an LH surge, and a surge can last for 1-3 days. So if you stop testing after your first positive you might not be maximising your BD opportunities IF your surge last 3 days, with Ov possibly 6-48 after that.