That depends upon what time of year you are walking and from how afar you plan to start for the final walk into Santiago. Provision of that info will provide more informed responses from the experienced members here.
Despite walking in the off-season, I have found arrival in the afternoon to place one in a long line.
Not being a big fan of queues, I tend to savor my walk into SdC, get lodging arranged and then find a bite and a beverage.
Early the next morning, I'll give St. Jimmy a hug after visiting the crypt and thence find breakfast. By then, the Pilg's Office is open and there are no lines. Plenty of time to walk the town before the Pilgrim Mass at noon.
This past March (the 8th, I think), I arrived at 17:30 - no lines! I was only at the office to check out the new location but, what the heck, I was in and out in five minutes.
Buen Camino!
B
Thanks for your reply... Planning to arrive this Monday ( June 20) with a short walk in that morning from Lavacolla (10 km) .