Thank you for the information and your question. I, unfortunately, wouldn't have access to any actual numbers or percentages of Reservists who are successful at reaching sanctuary while on active-duty orders. However, I do know that it happens and can discuss the law and Navy policy.
Navy policy is that a Reservist not receive active-duty (other than for training orders) unless they are under 16 years of service when they start that duty. However, the law, as you might be aware, under Title 10 United States Code section 12686, is that once the member is on those active-duty orders that they cannot be involuntarily released from active-duty without permission of the Se0cretary of the Navy. It is important to note though that if the Reservist is receiving orders that are for less than 180 days, the Secretary can require that sanctuary be waived by the Reservist.
You don't say for how long your orders to active-duty will be, but if it is less than the period of time you need to get you over 18 years, then it will really be up to the needs of the Navy as to whether they extend you. Like I mentioned, it does happen, but because of budget and DOPMA/ROPMA numbers caps, it could be hard to achieve. I suppose if you in a hard to fill billet, or specialty that would help.
Please feel free to ask for clarification if needed. If none is needed, if you could take a moment to leave a positive rating in the box above, I will receive credit for assisting you today. Thank you