Congratulations on #7! We have had 5, the last one is a foster son of 13.
What breed of sheep are you spinning? What is the lock length??
Can you spin 'in the grease' ... you bet! First you'll want to warm that fleece up, either by laying it out in the sun, or as I do, when I spin in the grease in the winter months, by putting it next to the wood stove.
When the lanolin is warm and free flowing, it is wonderful to spin!
That said, you should make sure you have as much VM (vegative matter) out of the fleece as humanly possible!
It is said you will pick VM out of home spun yarns at least 4-5 times:
1)When hand picking
2) when picking
3) when carding
4) when spinning
5) when knitting/crocheting/weaving
What I'm saying is the better you clean your fleece of VM, the easier it is the work. Sometimes this means scouring your wool. You don't necessarily need to take out all the lanolin though!
I have a few links on my spinning page (still under development - I've had enough time just to put some of the links I don't want to lose) on cleaning raw fiber.
If the fiber locks are consistantly breaking at the same length, it could be due to stress on that sheep. Anything from weather, location or feed changes during that time when the lock was growing will affect how strong the lock is and how easily it breaks.
If you have any questions, just holler!
I'm no expert by any stretch of the mind, just a lonely spinner/knitter/crocheter/weaver who learned by books and trial & error