Thanks - but here are the steps that I was looking for validating the title field in the "create page wizard":
1. Go to CRXDE and copy the /libs/foundation/components/page/cq:dialog node up to your own base page component
2. Then under the copied cq:dialog node go to cq:dialog/content/items/tabs/items/basic/items/column/items/title/items/title
3. Set the property maxlength of type Long with value to whatever you want to restrict it to
4. Save
5. Refresh the UI and try to create a page and see that now the title field length is restricted
Also, just to test and see that this solution works you could first try setting maxlength on the node under /libs/foundation/components/page/cq:dialog/content/items/tabs/items/basic/items/column/items/title/items/title