As someone who is (overly?) honest/careful; this could be a con. Also, if you're able to, bill by the day.
This isn't really how it works though. If you find "getting called in" (what does this mean?) to be terrible, you should be charging more for that service. You should be in control.
The whole point is to generate enough surplus value that your client signs the cheque, no questions asked, and is happy to do it. You shouldn't squabbling over hours.
A while back I worked at a consultancy that typically billed using a 15-minute granularity during standard office hours, reasonably rounded up/down. Unless otherwise contracted, outside of office hours the granularity increased to 1 hour rounded up. A 5 minute fix would be billed as an hour, a 65 minute fix as 2 hours, etc. It was also only undertaken for emergencies; general work requests would be done the next business day.
Generally all contracts were budgeted some number of hours per billing cycle per service. N full-time engineers would be converted to an equivalent amount of hours for the budget.
The result was that overtime was used judiciously and clients were rarely insisted on pushing big changes near the end of a day or on Fridays.
I bill by complete days now, so I don't take on work that is less than a day.
If I work half a day for a client, the next day I will work half a day in the rest of that job.
This still gives me the flexibility to not get bored in a single day.
This sounds like a day here means "about 8 hours" as opposed to "the work performed during a given calendar day". Makes sense.
I think that it is unabashedly a pro, because whenever you are adding value to the business and can defend it in an invoice, you're able to get value for it. Unlike when you are a salaried employee and the extra hours don't get you anything material (maybe noticed and provided with a raise. maybe).
I loved:
* the flexibility
* getting paid for every hour I worked (I billed by the hour)
* the freedom to choose clients
* having more than one made me feel more stable
* how close it kept me to the business problem space
* the ability to take time off
* the distance: I could roll my eyes and say "at least I'm getting paid for this BS" when there was political BS
However, after time I joined a team because:
* PTO is quite nice
* Insurance (in America) is better in general for employees
* it was great to be part of a team
* the ability to specialize in a way that is difficult as a contractor (I can be further away from direct revenue generation or product creation)
Highly recommend everyone tries this out as you'll have a much greater appreciation for all the components of a business when you are doing them yourself (or are responsible for them).